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!