Wednesday, December 30, 2009

The box for the hf-radio

Not much text here and especially none schematic!


There's a lot of stuff still missing in the receiver part.

- A better working AGC, have to check schematic again.
- Tone control
- Pot for volume control
- All the bandpass filters
- Pre-amp
- Attenuator
- Connect the mode selector (second bigger knob on the panel)
- Power supply switching for rx/tx
- Fine tuning the audio notch
- Add a variable filter....includes changing all the IF part....
- Other stuff missing....

In the future will post all the schematic. now, it's like this:

Input filter: will be from the GQRP design of bandpass filter
RF preamp: will be from K2
Front end mixer: From the ARRL 14Mhz receiver
First amp: From 14mhz receiver but will put equal to the K2 transceiver
IF amp: from ARRL receiver but output is equal to MC1350 datasheet
BFO mixer: ARRL...
BFO oscilator: From Minipig receiver
Audio amp: ARRL...
Notch filter: From QST design
Audio amp: ARRL...
VFO: Hands electronics DDS-3
VFO amp: Can't recall now...

Happy new year!

Tuesday, December 29, 2009

140Km/h antenna

This month, on the 23, my family QTH area sufered from a small winter storm.
I don't have a real shack there, just a small marine band receiver and a homebrew VHF antenna based on the design somewere on this blog (
The small antenna survived 140Km/h peak and 80Km/h average winds recorded by a nearby navy weather station.
The satelite image is at the time of the storm pass.

There were a lot of damage in the area including some roofs that disapered and around 20 very high voltage electricity poles (10 tons each) putted to ground, luckily there were no personal injuries.

Will put later on the antenna images.

Wednesday, December 23, 2009

Power meter IC arrives

Got this in the mail:

Sorry for the crap photo...I do solder better :)

Santa did come early this year and brought me an AD8307.
Since I will be busy with other stuff probably will only make the power meter latter on. Will also use the Linear IC for a full DC to dayligh power meter.

Meanwhile I've been searching for a nice tone control to place on the hf-radio and that will be the next thing to put there. The AGC is ready but I still have to put the TL074 on the IC socket , there is no LM324 in town so the TL074 will fit nice, I hope!
Also changed a litle bit on the IF amplifier part and the output of the MC1350 is now acording to fig 7 on his datasheet, the values I placed were for 10.7Mhz but looks like it is working whit less noise... probably will change the input part also.

Monday, December 21, 2009

HF radio (5)

Had some time to improve the radio a little bit and added a notch audio filter. Had to change the opamp since it is hard to find the RC4134 so made the lucky guess of replacing it by an TL074.

This notch is not bad considering I didn't matched the resistors nor the goes almost from 0 to 7Khz, will change that latter on, I only need to go to 3Khz.

After seeing the images on the computer I discovered the I have an audio bandwith of 7Khz.... as you can see in this photo (the notch is around 3.5Khz)
The signal you see at around 1.5Khz is from an transmission that was on 10.100Mhz and is were I make the air tests since it sits almos all day there and has a big signal.

what's is the cristal filter doing? The problem is not the cristal filter but noise induced by the MC1350 (I think). Probably will upgrade the schematic to look like the Elecraft K2 in wich they have a small cristall filter after the MC1350.... now I understand why they placed it there.

Here is an output of my TS-50 appliance...see the cut at about 2.5Khz?

On the radio, I placed a LSB/USB selector based on a diode switcher and changed the feedback capacitor on the oscilator because it was not starting all the time, the oscilator itself changed from a double 2n3904 to an 3904/06 pair similar to the minipig-10 transceiver bfo (the one at 8.064Mhz), just removed L20,L21 and C57. Didn't used for now the diode switching part after the vfo.
Here is how the board looks now, there is already in place the AGC IC support near the cristal filter... that will be made another day:

Top row from left to right: Notch filter, BFO oscillator, AGC IC support and bellow cristal filter, VFO buffer.
Bottom row from left to righ: Audio amp, audio pre-amp, BFO mixer (SBL-1), IF amp (MC1350), relay cristal filter switch, first mixer amp, first mixer (SBL-1).

Last minute update: I got one LTC5507 hopping to make a power meter that goes to Ghz....(I allready bough an AD8307 but waiting for it's arrival) problem is I had no idea how small the component is... anyhow will make the power meter if I can find a soldering needle.. the IC it self is the same size as the pen tip....the same size as an SMD resistor... and has 6 terminals!!!!

Season greetings....

Wednesday, December 16, 2009

Meter repair

Some years ago I grabbed my tent and went to Germany to the ham radio exhibition. The idea was to leave the tent and on the spare space bring a lot of junk.
I did managed to bring the tent and the junk... although at the Swiss airport (I went via Zurich) control was difficult to put everything inside after removing the tent to explain what was that on the x-ray..... they weren't interested in the wires, valves, meters, etc... oh well.
Unfortunately 2 of the meter I bough were damaged... can't trust some sellers.. today I did managed to repair one, some soldering's and voila... some one had already tried but without success since some nut's were inside wrapped in paper. The other metter was a Russiam metter and the moving coil was in open almost impossible to repair, will keep the magnet.


The idea was to use the meter in my future rf power meter but honestly it is to big for finding a nice box. Will be used in some other project. This meter must had come from a "m Ohm" meter, don't need one for the moment but let me think that it must had used a Wheatstone bridge or something similer for measuring.

I have one 150uA meter from the "Westinghouse Electric Company" and probably will be the one to use, after all "Mr Westinghouse" was a defendant of the "Alternate Current" although for some more "dBm" that I intent to measure....

Monday, December 14, 2009

HF radio (4)

...The first sound.... not quiet what I was expecting but already some reception. The radio is a little deaf (no rf preamp and no rf input filter at this moment).
Made some more tests after this video, changed the first if preamp schematic a little bit but not much improvement, still have to check levels on sbl-1 mixers and verify all the if gain part of the cristal filter and mc1350. Basically at this point is copying equivalent to S2/3 on a commercial normal transceiver... I want a little more, also I already verified that the lower the noise the better to distribute the gain so will separate all the oscillators and different modules with some pieces od PCB.


Here's is another video at 20m band. Note that I changed the cristal filter relay in the middle of the board for a smaller one.


Saturday, December 12, 2009

HF radio (3)

Still "fighting" to put the DDS programing software accessing the parallel port under "dosemu", will try now to boot DOS native...if I can find a diskete....

--Adendum--- Found a diskette with DOS, saved dds software on it, changed to another computer, changed parallel port to standard, messed with the cables... and voilá! Programed with a fresh 9Mhz "IF" more or less some little herts...I am happy -- end adendum----

Meanwile made a new "rf test probe", smaller with a less drop diode... now I have more 0.1v on my measurings. Previous diode has a drop of around 0.40 this one has 0.30 more or less... but still I have to calibrate the dam thing. I measured my DVM internal impedance.... it almos reaches the 30MOhm... wich lead me to doubt on the metod used... so I made the probe assuming the impedance was 11MOhm.
You can see in greater detail the original design:

Meanwhile I had to move the shack power supply near the computer so I can program de DDS and found out that actually the power supply wasn't a laptop power supply inside a box,....I was almost sure it was..., after all it was a conventional power supply with an 7812... the other output is a varialbe LM317 type, no wonder that sometimes it shuts down with lot's of boards beeing connect.... oh well it was puttede in place an worked for so many years that I forgot completly.... the box is of "Chivas Regal" brand.... will rebuild in one of this days. The paper inside is the schematic... in case I forgot what was done....It was the case!

Thursday, December 10, 2009

HF radio (2)

Now that I connected the DDS3 vfo...I just found that 7 years without use made it to lost the registers.
It was bough in 2002 and since then it was only connect 2 or 3 times so it's natural this happened... the problem is the kit is no longer sold and the software came on a 3 1/4 diskette. I was lucky, managed to read the contents (Linux command "mcopy a: .") and saved the programing software to a new disk.... but there is another problem, the software runs in DOS, I don't use DOS for some 12 years and I don't use the other operating system that supports reading some DOS applications.
Linux has "dosemu" a dos emulator. I can now run the software but still didn't tryed to programe the equipment. DOS is not exactly the "shell" ins fact is "freedos".

The vfo for now is runing with an IF of 14 Mhz, it came programed when bough with an 9Mhz IF... anyhow made some tests with vfo on 17.5Mhz and my dip metter on 8.5Mhz (8421Mhz exactly)...there are some 79Khz diference I can't yet explain for my 9Mhz IF (17.5-9=8.5 != 8.421).
Almost for shure something is working in the radio since the audio is only when the osciltor is close to the wire conneced to the sbl-1 first mixer input, I am not so positive regarding the levels on the mixers... previous experiencies show'd me that big signals always are received, problem is the smal signals... I need to make an acurate power meter!!! Does anyone has a spare AD8307 that can send me? For a reasonable price of course :)


A photo of the building process.... the first mixer, the if preamp coil, pre-filter coil, relay for cristal filter switch and 9Mhz cristal filter.

Tuesday, December 08, 2009

HF transceiver (1)

I am building an HF radio....It's my third atempt! I built (soldered) the "Speaky" but never put it to use, built some modules years ago but never finished them, so it's time now to make one to put on the shack.

I am using mostly parts from the schematic at: - (arrl 14 Mhz transceiver) but converted to multiband.
The vfo part will be a DDS3 from Hands Electronics and the bandpass filters from "Gqrp" design using Toko coils. VFO amp (if neded) will be the one from "Analog Devices" application note AN-557 (a simple 2n3866 amp).

I built the IF strip and it looks that is working nice. I am now testing an BFO cristal switcher so I can have LSB and USB. For now the LSB cristal is just 140Hz away from the correct frequency (8.9995)

In the video the rf generator is around 40cm from the 9Mhz if input. I still have no rf front end done except the first mixer.


There are however some "error's" I found on the schematic:

- On the second sbl-1 (connected to the bfo oscilator) the IF pins are switched , replace 3 and 4 by 5 and 6 and vice versa.
- The caps on the BFO oscillator first transistor should be 47 and not 470, probably something around 33 should work also.
- T6 ref. doesn't have the number of turns for the secondary, I am using 2 for the moment (just testing), on my "not calibrated" power meter gives 0.2v (=~ 1dbm) so I will increase later one.
- I replaced the NEC99532 transistor by an 2N3866, still have to test if it's ok.

Friday, December 04, 2009

Some metal work.

This will be the box of my new/old project. An all band / all sort of controls/ ultra high performance (basically similar to an ne602...) hf transceiver... I have for some years an dds-3 kit so it will be used for vfo, also have an 9Mhz filter that I bough some years ago as the bfo cristals. The bandpass filter design is somewere on this blog.
First mixer will be an sbl-1 and second probably the ne602 or another sbl-1. The design is a mix of several designs and will be used the ones that work beter.

Thursday, December 03, 2009

B box

First: I have no financial interests in this brand.
Second: Enclosures for experiments are getting everyday more expensive.

Went for lunch at a little restaurant and found they have some nice napkin holder....
This will be the perfect box for some small circuit although it's plastic on one of the covers and have small holes for the napkins it will suit fine.

Now they have one less.... have to go there again :)

p.s.: the box and the napkins were offered case you were thinking different!

Sunday, November 29, 2009

Bench clean up

Not much time for electronics so not much postings here.
Had a little time so decided to start on the new Si570 kit. It will be used for the VHF receiver exclusively. The other kit will stay in the Airband receiver...or will be used as testing generator...
for this kit assembly, since most componets are smd, one needs to have a clean bench so on to the cleaning.

From the mess to clean up:

The Si570 kit:

Some testing boards and Chinese store radios used for parts and frequency meter.

After this is done I have to put a lot of projects in boxes and make some calibration on my meters...those will be my future projects.

Saturday, November 14, 2009

HF antenna splitter

It's Saturday afternoon and I am a little nothing like heating the soldering iron and make something interesting...or not....

Some time ago I found some receiving antenna splitter schematics and now decided to have a go on it.... I already had tested an antenna splitter ( without luck) using an cable tv unit. This one worked like a charm, of course port isolation, losses and other operational parameter were not tested...

Schematic came from this nice article:
I just changed the number of turns to 10 on T1 and T2. The resistor is a 100 Ohm one. Today propagation was on the nice side and so there were plenty of signals coming to my humble 17m band wire dipole (homebrew of course).

In action both receiver on the same frequency (actually 2.5Khz offset):


Another one with one receiver at 7Mhz and the other at 14Mhz:


Didn't tested for now on the low and high bands since but I am sure it will have success also. Also I didn't notice any interference from both radios except a small glitch when powering on.

Thursday, November 12, 2009

5-5.5Mhz VFO Buffer

Now that that the vfo looks nice and works nice....I must found a better variable capacitor, this one only has reduction of 1.5:1, the "rit" pot could help the lack of reduction on the capacitor but I want something nicer... so I will put the assembly on the "finished but no use for the moment" rack.
The output without load is around 1.9V measured with the homebrew rf test probe... ( Probe )

The VFO buffer schematic

Drift from cold start:


Not bad hum? Considering the the box isn't closed and there are led's working as varicap's in the circuit.... also no capacitor was chosen for their thermal characteristics, only for their value.

There is some cw in the video background (this vfo was not connected to the radio), I was trying to copy the "no power transmitter" Atlantic crossing ( but I guess this transmission was not them...

Saturday, November 07, 2009

5-5.5Mhz VFO

For my FT-102 I have been using the FT-107 VFO but it's like killing flies with a cannon since I make no QSO's at the moment and it could be used for the FT-107. After decided to use an homebrew vfo it's time to build one.
Transistor is a 2N3819 (no MPF102 in the "LES", local electronic shop). Variable capacitor is salvaged from an old radio and honestly I didn't measured it, also the capacitors of the tuned circuit were more or less dropped in the circuit til I have the 5-5.5 Mhz range. Toroid core is an T50-2, black and red with 30 turns and "middle" point at around 8 turns from ground. wire is 24 swg.
I reduced the power supply to 6v to try to improve on the stability. Since I didn't measured before I can't give you info if it did improve!
The "varicap" diodes are 2 red led's and give me around 10Khz offset in the highest vfo frequency (around 5.6Mhz). It tunes from around 4.9Mhz.
You can see in the video the initial drif. I hope that after placed in a box it will get betther. Anyhow made some tests after warming up (and the frequency counter removed) and it doesn't look that bad.


Not finished yet since I still need to put the buffer and find a nice box, will do that when needed.

UV916 tuner receiver based - Some tests

it's not complete but can't wait for it so made some tests, although not exactly very scientific but just to check if there is some signal on the output of the tuner.
I am not quite sure on what is the default frequency on the tuner since the programing part is not yet finished but since I get some signal (read: interference) out when there's some input it's a good sign.


Another video of what output looks like (actually sounds like) when I inject 88Mhz (I suspect it could be some harmonic here).


Wednesday, October 28, 2009

UV916 tuner receiver based (part 1) - Power supply

For the UV916 tuner one needs an 33v power supply. That's a small problem, my bench power supply only has 12v (more or less). Digging for an easy step up converter (read: search for what components were available locally) I found the MC34063 IC that my local electronic shop stocks as KA34063. After reading the datasheet I came up with a schematic.

Now it's a question of start dismantling some computer power supplies to find the 170 microH inductor since I don't feel like't to make one. I still don't have the IC so for the first time the schematic come first!
The local store doesn't stock the BYV10-40 diode but stocks the 1N5822, they look similar (10-20% values) in the datasheet so I will give it a try.
This is my first "switched" power supply so anything could hapen!!!

Replaced the 47K resistor by an of 33K and the 1850 ohm for an 1K2 in series with an 220ohm variable pot.
Diode was replaced by an 1N5819.
I did wind, after all, the toroid, it was salvaged (along with the output 200V!!! capacitor) from an old computer power supply and has 82 turns of 24swg wire on a yellow core... probably less turns would work also.
The 0.22 Ohm resistor was made winding around 40cm of wire.....It works.
Placed an 56k "bleed" resistor in parallel with the output to discharge the capacitor.
After following the data sheet on the MC34063 and making the schematic I found an online development aid for the IC at:

Tuesday, October 27, 2009

UV916 tuner receiver based (part 0)

I was given some obsolete electronic equipment, namely some VHS video recorders.... I accepted thinking in using the boxes for some project.... but there's more than the box, a big collection of components including an UV916 tv tuner. Some time ago I came across some spectrun analizers and receivers using this tv tuners, now it's my time to test.

First thing to do is desoldering the most important components, I will not mind for now with resistors and capacitors, just the ones I could use on "rf", like the tuner some filters, cristals and inductors.

Now I have to look how things are connected:

And the TDA9813 match's in the datasheet from what I draw from the PCB circuit...VIF and CIF inputs I thing has something to do with bandwith beeing one of it mpeg4...

Here's another IC's used in other type of VCR's... looks like they are all almost the same...and the technology matches the components I removed....there's also two exits on the saw filter bellow...

Now I am having the idea on how to connect everything.... The front end will be the tuner next the saw filter then an MC3361 based FM receiver from 30 to 40Mhz so I can fine tune since the PPL in the UV916 has step's of only 62.5Khz. The UV916 will be computer controled...

Ther's is a nice site with one completed receiver based on this tuner at:

....this will not be an easy job to do but I will give it a try.... but will take long for sure.

VHF FM receiver with Si570 VFO

Now I have two receivers working in sync with the same VFO, the airband receiver and a VHF FM receiver based on the NE602/MC3361 combination, they have separate antennas but a common audio amplifier.
The MC3361 circuit is based on the one at:
I just replaced the TA7358 front end for an NE602 front end similar to the one on his datasheet. The 10.7 filter is a salvage unit from a chinese store radio.
Unfortunately the squelch is not fully operational and I will have to check again the schematic against the datasheet.

Here working simultaneously with the AM part of the circuit:


As soon as I build the other Si570 kit that arrived probably will place it in another box and not in the airband receiver box. Initialy my idea was to make an coil vfo for the NE602 but since I have the Si570 it will stay more acurate and frequency stable. Tried to replace the discriminator coil for an 455Khz ceramic cristal but didn't worked good, will try one of this days a combination of an commercial inductor and a capacitor since discriminator coils are not the easy thing to get around town. Probably an 360 microH with an 340 Pf capacitor will ressonate at 455Khz.

Friday, October 23, 2009

New IF for the airband receiver

I changed the IF of the airband receiver, now is 10.7Mhz for the first conversion and 455Khz for the last one, that way I can now add an FM 10.7 IF to the circuit, being double conversion on AM an single on FM in order to optimize the Si570 kit (AM airband and FM 144Mhz), probably will make also an front end and IF for 50Mhz ssb.
The circuit is a simple NE602 with an 10.245Mhz cristal and the filter is an 10.7Mhz cristal front the first mixer to the secound mixer, case connected to ground and a paralel capacitor in the secound mixer input (pin 1 on the ne602).

Sunday, October 18, 2009

What's next

Now that the airband receiver is done (closed inside a box) I am a little bit out of ideas on what the next project should be....

Ok, I have some boards left during the development of the airband receiver, am thinking in the one that has the TDA1072, it gives a nice SW receiver.... one of the audio amps probably will also be used and as soon as the new Si570 kit arrives will be used for an VHF FM receiver with the MC3361 but them what... there are some boards almost ready for an HF transceiver and the "Speaky" ssb transceiver is waiting for the final touch.

I am opened to suggestions...

Friday, October 16, 2009

The Airband last!

...Not quite but enough!

Yes the Si570 kit returned from the "repair" (thank you Kees)... well it was more an operator issue than a repair, anyhow the thing works and I can finish now the airband receiver and move on to another project. After finishing the new squelch circuit (I changed from the TDA1072 to an TCA440 if) and put the boards in a box, I will consider this project done.
The receiver is not perfect but works to the minimum level I wanted, in the future probably will rebuild the input filter making it simpler.

The final circuit is similar to the ones I allready posted on previous articles so will not put again heres since I didn't draw it completly. Main features are:

Neosid coil rf filters.
BF981 rf preamplifier
NE602 mixer
Si570 VFO - kit from Kees, K5BCQ (can't get anything beter for the price)
TCA440 AM demodulator on 455Khz
LM386 (what else?) audio amplifier
CA3130 comparator for squelch circuit (shorting audio input via pnp transistor on act).

Sensitivity: enough
Audio power: enough

Here's the "beast" working, sory for the audio quality.


...there's a new Si570 VFO kit crossing the Atlantic.... but that is for another day...

Sunday, October 11, 2009

Multiple receivers on one antenna, some tests

Recently I came up with an interesting problem, I have more receivers (note: transceivers working as receivers) than antennas so I have sometimes to interchange antennas between them, wouldn't it be nice to split an antenna to several receivers.

Saw some interesting circuits in the internet but didn't tested any of them but I have some cable tv splitter's that would be nice for the job, here's the testing circuit:

Splitter is an "Teka" brand model 4302S/P-15 2-way tap 5-2400Mhz

Some problems with my testing:
1 - My signal source is not 75 Ohm
2- I didn't terminated all ports
3 - I don't have an rf voltmeter I can trust, only a simple rectifier probe connected to an DVM.
4 - I only tested at VHF

Anyhow I still didn't tested connecting to an receiver, probably some acceptable results could be found but I am sure only for high level signals.
One interesting part is that when connecting directly in the "power pass" output I have more output (on 145Mhz) than the signal generator directly connected to an dummy load....oh well that's the problem of not having accurate meters....

Some circuits that probably will work (for HF):

will test them one of this days....

Saturday, October 03, 2009

Goodie's from the UK

My good friend Per from Sweden, working in the UK, came for a visit to Portugal... ain't we in a global world?
He asked before if I needed something from the UK....! A quick look in the website of an UK electronic shop and I remembered my enameled cooper wire was on the short side and that I can't get locally nice buttons, so here is what I got. Next time he fly's here I will ask for an lousy t-shirt!

Now I just have to get some free time to give this some nice use.

Wednesday, September 30, 2009

External VFO controller for the FT-102

Had been without time so no updates were made on the last days but today I got some free time and on we go with the projects.

I decided to call this project an external vfo controller for the FT-102 since it doesn't mimics all the functions of the original external vfo but it is adaptable to any external vfo in the range 5-5.5Mhz with 130mV (or something like that) output powered by an 8v supply. Mine was an FV-107.

I did lost some time making this simple schematic just because when reading the FT-102 schematic I was seeing the ouput of a simple zener regulator as the imput making no sence to as the FT-102 controls the external vfo, in fact as soon as I placed the din plug on "ext vfo A" of the FT-102 it came to light. When you connect a plug in the external vfo A of the FT-102 he simple disconects the power supply from the internal vfo, ther's a connection so you can power it again. That's is how "control" is done. Ext vfo B it's just used to give indications on the mic buttons and internal reference oscilator case you use an pll.

Another issue that arrived is that the 12v present on the ext vfo plug aren't enough to power an hungry FV-107 with all the lights on ,so I just used the vfo part and not the christmas light's part, after all I just want ot make split's biger than 10Khz given by the internal vfo rit control. I still placed a capacitor to minimize power on current but it wasn't enougth, probably changing to an external power supply would solve this issue but wanted to keep it simple.

I think the "external vfo A" din plug on the FT-102 is not a standard one but you can "convince" a "normal" din to fitt there, assuming it has the same number of pins!

Here the schematic and the equipment working on an action video.


As soon as I found a cheap reduction drive and a nice capacitor will make an vfo smaller than the FV-107 so it can take less space and free it to another project.

By the way, I did this just to see if it was possible since my last QSO was more than an year ago, I gess I prefer to brew and no to chat.

Thursday, September 17, 2009

FV-107 to FT-102 external vfo (FV-102)

One of the Yaesu FT-102 problems besides the relays is to get an FV-102, the external VFO, except this issues it's a nice radio at least better the ones I far!. I dig around for a used FV-102 unit but the ones I found are too expensive for what I wanted to pay for legacy IC's in a box. I had two chances, to make an external VFO or to use an allready existing VFO from other radio. Since it's hard to make or to find good tunning capacitors with good reducion drive and dds/pll/etc is out of the question, to keep some signal purity, I went to the secound option; use an FV-107 as vfo for the FT-102.


The circuit is not finished yet so I will post the result when a repetible and clean assenbly is done. VFO interface and control is not completly linear in the FT-102 and with schematics on paper it took me some time to figure it out on what had to be done. See the video to see what is possible allready.

Wednesday, September 09, 2009

PIC packet decoder

No big story here, at the same time I was looking for an APRS tracker found some schematic for an pic APRS decoder so why not build one also, I have no use for it at the moment since I make APRS on the TM-D700 but will probably incorporate it inside one of my vhf receivers or to take along on vacations.

I didn't compared side by side with the TM-D700 decoder but without optimization and using the ruber duck antenna inside house with the TH-F7 handie I think I got arround 20% of the packet's transmission. Probably with a good radio and some optimizasion the circuit will get 80% of it.
For testing I used Linux "minicom" software at 9600 8N1 without software or hardware flow (there's no flow, just receiving). The radio was with audio at mid volume seting.

Got the software from:
Select "Simpler one chip ZCD decoder Both PC and GPS versions" (Simple decoder" button). Download de zip file, all the necessary files and schematic are there and also improvments for the circuit (I didn't do that).

For the pic programing I used the following command on a linux shell:
picprog --input-hexfile simpler_rx8.HEX --pic /dev/ttyS0 --burn
The pic programer hardware is at: in this blog.

The PIC is an PIC16F628-04, I tried to use an 4Mhz ceramic filter as the oscillator but only the quartz crystal worked.

Thursday, September 03, 2009

The good and the bad news on the airband receiver

The bad news first.... my Si570 kit is broken... not completely but can't see problem with it, probably the chip is dead.

The good news... I made an ne602 vhf vfo to temporary replace the kit with an air coil and and some more components and can finally have acceptable reception on "Volmet" frequency also changed the mixer to an ne602 and the AM demodulator to an TCA440 that I had bough some 6 years ago and never had used it :)

Will post some pictures the next days since right now you will only see a bunch of wires connecting the boards and the vfo is not as stable as I want.

I am quite sure my previous unsuccessful attempts were some how related to poor construction technic and bad IF selection.... the frequency I was interested was 126.400Mhz, if you put an IF of 10.7 one of the products will be 113.7 and the other will be 105Mhz... right on top of a local FM broadcast frequency... now the IF is 455Khz.

Design is based on this one at:
except my rf preanp and vfo is diferent and there is a resistor and capacitor from ne602 to 455khz filter as per ne602 datasheet.

Here is the video. First image is the audio amp/speaker in the box then moving the camera do the left the rf preamp and vfo/mixer and more to the left board the tca440 demodulator, the big blue cap between pcb boards gets the IF output from the ne602. In the middle of the video you can see my finger de-tuning the vfo coil.


Sunday, August 23, 2009

Sunday soldering

Never, ever do soldering at a Sunday, instead go to the beach, the mall, the mountains, whatever!

Just broke one PIC16F84 on the aprs tracker! Why? A faulty 7805, probably a fake 7805, I am pissed of. Happened when I was rewiring the board. When I get the 7805 from the 78/9XX drawer it was different from all the others, it had a more glossy finish, I even tough that it might be broken but was the the first one I found in that mess. I already saw a lot of them in open circuit but this one was on short an powering the PIC from 11V, the voltage from my power supply; even so the circuit worked but not for long and today it came to an halt. I should have know, always measure the voltage after the regulator, it was getting to hot for the total circuit dissipation and was the only component getting hot. The interferences on the handie were also strange! Some outputs do work but not the squelch/audio part and can't read now the PIC contents.
Tomorrow will buy another 16F84 to replace this one. Everything was against me and even the handie I was using to make transmission tests lost the battery charge when I left to test the PIC on the programmer, it's now charging. Lost the patience for the day!

Anyhow... surfing the web to relax a little bit I found some "blog's" from people I previously exchanged some emails regarding homebrew; Al, GM1SXX (, Bill, CU2JL ( and Carlos, CT4ER
( They are nice people and have nice web pages with interesting information.
Al was also brewing the "Speaky" transceiver, exchanged some emails with opinions, Bill made an DSB transmitter and asked him some info and I used a bfo schematic from Carlos when I was making my first, never finished, HF transceiver.

Have a nice week!

Thursday, August 20, 2009

Mail order components

Got this in the mail:

Now I can go on with the airband/vhf receiver experiments with new input and IF filters.

Silver wire for testing diferent vhf coils, Neoside 5061 (6) variable inductor for input filter (2 filter, one for 144 and the other for 126Mhz), four 455Khz filter plus two 10.7Mhz, different bandwidths. Two (yellow) 455Khz coils for FM discrimination, tree pig noses for an rf amplifier. 2 Neoside cores to make an vhf oscilator and a micrometer just for fun :) Not cheap but could not get it here localy so bough at Barend's shop in the Netherlands, I like that country! Barend's shop is at:

Stay tuned!

APRS tracker (Tinytrak)

After programing the 16F84-4 PIC I placed it on a perforated board and start soldering.
This time no ugly construction technic, only ugly, because there were to many pins to solder on the PIC, this method is easier for this type of circuit.

Schematic and software are here:
Cable connection for my handheld (TH-F7E) from here: (it's also on kenwood manual.) the radio is set as TNC for the external plugs, could be set as speaker, tnc or pc control for programing.

It was not that easy to get data from my GPS (Garmin GPSMAP 60Csx) since the GPS data signal was not being received by the PIC it's the old war between ttl/cmos/rs232/482....whatever incompatibilities :)
So I made an level converter a simple comon emitter with an 2n3904, any npn will work, (incidentally is also an signal inverter) so I could feed the data to the pic. Strange is the on the Garmin side I have to place the ground to data out and data in on the pic to ground..., is Garmin wrong on the manual? It's the pic software or it's because of the inverter circuit.... should work on other gps without inverter so it's not on software.... oh well...

The LM7805 gets a little bit hot for my taste so will lower the input voltage putting another regulator that way I will get the same dissipation but will be divided by 2 devices. Eventually will be powered by a 7.2v source.

Programing was almost flawless except for a small short between tracks on the board that was not letting me to read or write the PIC.
The software was "TTconfig 1.3" but had to install some perl modules needed:
Tk::TFrame and Time::HiRes
basically nothing more that issuing the following command: perl -MCPAN -e shell
and then this one: install Tk::TFrame
and: install Time::HiRes
questions? the INSTALL file on TTConf-1.3

Made some testing tone transmissions, looks clean althoug only tested with the tone features, as soon as I remove the pc interface will place the gps input again. next time I will place a 9 ping plug because it's easier than soldering the cables for testing.

Now it's just to put it on a box get a data plug for the Garmin unit and start beaconing aprs... will use the rest of the perforated board (it was expensive 6.12€ for a 100*160mm, used about 1€ on the tracker) for an aprs packet decoder.... but that's for another day.

Friday, August 14, 2009

PIC programmer for APRS tracker

I am getting "digital"!!!

Funny thing was when I studied electronics I always considered digital being a subset of the real electronics. Having already done some digital circuit's I did see that was not all that 0 and 1's.

I wanted to make a bicycle mobile APRS setup, considered buying one allready made but that is half the fun an double the price. Searching for some aprs trackers settled by the standard "tinytrack" got the software and bough some PIC's (eventually some will get hurt!)
For the PIC programing you have to have a PIC programmer... decided to make the simplest (not always a good choice) PIC programmer I could find.

This time I made the circuit in a prototyping board since I was easy to remove the pic after programing and "zif" socket's were out of stock in my local electronics shop. The board still had in place one 555 IC and a photo transistor but honestly I can't remember what was it... an light controlled oscillator or something similar..

The circuit worked first time (had no 5V6 zener so placed a 5V1) but before real programing I had to compile the picrogr-1.9.0 software on my primary Linux system, if you don't use Linux, IRIX, AIX, SunOs (love them all, but Linux is cheaper) or any Unix like....I am sorry for you, can't help you, you are on your own with that buggy lousy operating system called.... :) I even can't write it's name but starts with a "W".

On a shell you can do like this, assuming you downloaded the picprog software (Thank you Jaakko Hyvätti
for the software):

gunzip picprog-1.9.0.tar.gz
tar xvf picprog-1.9.0.tar
cd picprog-1.9.0
make dep
make install

Connected the programing circuit to the computer first serial port ( /dev/ttyS0 ) with the PIC16F84-4 already in the circuit and decided to read it's contents:

[root@work2 proj]# picprog --output 16f84-1.hex --pic /dev/ttyS0

Picprog version 1.9.0, Copyright © 2008 Jaakko Hyvätti
Picprog comes with ABSOLUTELY NO WARRANTY; for details
type `picprog --warranty'. This is free software,
and you are welcome to redistribute it under certain conditions;
type `picprog --copying' for details.

Trying realtime priority 1
Bound to CPU 0
Using >1 µs delays. --rdtsc may work for faster timings.
/dev/ttyS0: id 0x0560: detected pic16f84a version 0x00
Device pic16f84a, program memory: 1024, data memory: 64.
Reading program memory,
reading data memory,
reading id words,
reading fuses,

This will create a file, "16f84-1.hex", with the original contents of the PIC.

Now let's write!!! but it's better to erase the blody thing with the following command:

picprog --pic /dev/ttyS0 --erase --burn

If you don't follow this step you probably end up in a "ff0002:unable to read pic device id" error... I did...

Let's do the real writing now:

[root@work2 proj]# picprog --input-hexfile TinyTrak_1.6.hex --pic /dev/ttyS0 --burn

Picprog version 1.9.0, Copyright © 2008 Jaakko Hyvätti
Picprog comes with ABSOLUTELY NO WARRANTY; for details
type `picprog --warranty'. This is free software,
and you are welcome to redistribute it under certain conditions;
type `picprog --copying' for details.

Trying realtime priority 1
Bound to CPU 0
Using >1 µs delays. --rdtsc may work for faster timings.
/dev/ttyS0: id 0x0560: detected pic16f84a version 0x00
Device pic16f84a, program memory: 1024, data memory: 64.
Burning program memory, 999 locations,
burning data memory, 46 locations,
burning id words, 0 locations,
burning fuses, 1 location,

Look's like it's done, next is to see if we can read and if the reading's output is the same as what was programed....and off course remove the pic an make the final board for the aprs tracker....

picprog --output 16f84-programed-tiny.hex --pic /dev/ttyS0 --ihx32


And the initial contents of the original file:


Looking to booth header's there are diferences but after it's the same so I guess it's ok... I will have to read more on PIC's to explain it but that's for when I found digital electronic's a litle more fun.

Now it's just a mather of making the final board for the aprs tracker.... but that's for another day.

Further reading: - schematic used - another diferent schematic - picprog info (RTFM) - tinytrack hex files

Some info on my Linux system:

serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
model name : Intel(R) Pentium(R) 4 CPU 3.06GHz
Fedora Core release 6 (Zod)
BIOS version 1.2 Flags 0x07 (Driver version 1.16ac)

Wednesday, August 12, 2009

HF and VHF preselector

Here's a simple circuit for the sunny days

Found a simple HF preselector circuit on the web and decided to try it out.

Basilcaly it's a variable tuned LC circuit between input and output...

I tested with 14 turns acording to schematic but only got preselection from 18 to 28Mhz then I add some more turns to 25 and got the 40m band also, tuning is very sharp, my variable capacitor is from one of those cheap radios and with all the plates in parallel to give about 240pF.
Take not that my tests were only against the antenna analyser, circuit input to signal out on the meter and circuit output to a dummy load, tuning was made until get lowest swr on the metter.

I decided to try an "air core" to see if it will scale to vhf, it works but in VHF work things must be well planed and it need's for sure an blindage of some kind since I placed between the antenna and my TM-D700 and I got more 1 "s" unit.... could also be because of metering circuit on the radio but probably was the air core was getting also signal. anyhow will test again against the airband receiver. Since my last testing on the airband receiver now I have too much signal...from a near by broadcast station and have to get rid of that.

The HF preselector:

The VHF preselector (same circuit but air core an less turns, 1-5-1):

Since it's still summer and very hot around the post's will slow down...

Sunday, August 02, 2009

A table top mic and the previous post...

Bough one table top mic! why? The price was nice and I need an microphone for my next transmitter project...eventually one of this days.
Of course I already opened it... it's an simple circuit with an sliding switch and a RC filter connecting to the Dynamic capsule. Will make an mic amplifier probably based on similar design to this one:

Size comparation with the Yaesu "something" (update: YD-148) mic:

Another photo:

Regarding the previous post circuit, if you place an 3pF capacitor connecting the "top" of L1 and L2 the circuit works better on the airband frequency (and others) but not with the performance I want... so now I will get some "Néosid" coils and adapt a 137Mhz receiver circuit to the 118-134 band...
Circuit will be similar to this one:

Meanwhile is summer so posts will slow down....

Wednesday, July 29, 2009

144 (mostly) to 28Mhz converter

I understood one thing, if it was easy for hams to do high performance equipment there were not many radio equipment brands.
Getting to an acceptable level of performance takes time and many trial an error experiences, since I have some time I will continue this quest learning something along the way!

As we say locally... "each shot, each blackbird" ...this one is another missed shot

This schematic it's based on parts from others schematics and the local oscillator is from the Si570 coupled trough an more or less 144Mhz dual coil filter (on the right of the pcb board but not on the schematic). The transistor is an BC547.

One thing for sure, my somehow lack of sensitivity on the receivers is mostly caused by the lack of experience in input filter build and of course lack of proper materials, for the coils build I am using wire from cat5 network cables and recovered from toroids of computer power supplies.