New "kit" in town

Got an frequency generator kit from a fellow ham locally (That was king enough to let one part go) which in turn he had got from "Kees" http://www.qsl.net/k5bcq/Kits/Kits.html
This kit is based on the Si570 chip and has an LCD, it can be programed to show offset or multiplier (for softrock radios). Mine is an CMOS version.

The idea was to have an stable VFO for the VHF airband receiver.

After powering up and verifying it was on frequency it was time to connect it to the TA7358, first mixer on the receiver.



I sent some emails to people I know have this kit but they only used it on the Softrock receiver without "normal" mixers like SBL-1, SA602 or TA7358, technically it should drive the SBL-1, but SBL's are on the expensive side and I had none in the junk box. So after thinking how to connect and many calculation later I found a way....(was joking about the calculation part). I decided the try and error method.
For the first time it worked at first.... just connected an 50 ohm resistor in series with an 10nF capacitor between clock + output on the kit and pin 8 on the TA7358.

This was on a little spare time I got so no further testing was made, but, I did listen to packet on 144.8 and some broadcast on 104Mhz. If your are trying to duplicate this please don't connect the varicap part on the airband receiver schematic! Obvious I think!

I still can only listen to FM modulation, no AM, I will check further to see what is the problem.

p.s. Found the "AM" problem....no problem at all, it's lack of sensibility on the filters (I think). If the signal is strong enough, it copy's good but noise to audio signal relation is low...

There is 3khz difference between the generator and the frequency counter.... so... which one is right ? :) reminds me that one of this days I have make an frequency standard generator for calibration.

VHF - Aircraft RX

Why would you make an aircraft RX when you allready have 2 receivers that can do the same?

..because you can? Because it's cheaper? Because you want get rid of any commercial equipment that in a few years it's more expensive the repair than buying an new one? All of the above!

After searching the net I found an simple receiver that suited me, it's relatively cheap to make, "it should work" just by looking at the schematic from my experience and it uses components that in 200 years should be around :)

This is the design: http://py2ohh.qrp-br.net/trx/corujinhavhf/corujinhavhf.htm


After initial problems with the VFO (read: diferent components than the original design) I now have an more or less stable VFO. Also some problems with de audio circuit now sorted. It works but due the VFO nature it's dificult to get AM because of frequency drift. I am now studing the inclusion of a more stable and external VFO. I can get FM due the nature of the design but only stations on high power so theres is sone issue on the gain/bandpass of the bandpass and rf amplificator filter.

The ceramic filters (10.7 and 455) were removed fron the low budget frequency counter radio, so their bandwith is too large ence the AM receptions has no great gain/selectivity relation. The VFO varicap I used it's an BB109 (I think, since there's no marks) laying around in the shack.
The front panel has one rectangular hole that was to get the low budget frequency counter in FM mode but since I allready broke 2 I have to find other "cheaper" alternatives... There's the big (red) an small button for tune and fine tune. I allready left provision for the squelch circuit and pot.




I also tryed with the schematic (basicaly the same) from: http://www.py2mg.qsl.br/receptores.htm see http://www.py2mg.qsl.br/Arquivos_PDF/CONTVHF.pdf
There are some subtle diferences in the way biased is done on the TA7358 from the posivite line to the 2.7uH choke and on the TDA1072, I think this last schematic (from PY2MG) is near the datasheets for the above IC's.

The box if from an old computer power supply the was broken. These make fine boxes for small projects and are dirty cheap!

Very low budget frequency counter

How to get an frequency counter for 6 Eur, and a bunch of electronic components.

At some point in time I needed an fm receiver for testing conditions for an receiving station for network radio broadcast. So being far from home I went to an Chinese store and bough one of those little radios, still works as off today. Then on the internet I found some articles about conversion of those litle radios to amateur use.... one of this days I went to the local low budget Chinese store an bougt one small radio. Here is the result.















Can you see the 10.7 offset? On AM de offset is 455Khz.

I destroyed the FM input after much soldering an testing on the "frequency counter" and bough another radio, the secound one only lasted the first test. the AM input is working on both...

The power supply are some 1N4001 diodes in series after an 7805 to get the 3v supply by droping in the diode, not elegant but it works.

There are also some nice componetes you get when buying this radio, 10.7 ceramic filter and 455Khz that I used for an aviation band receiver (but they are to wide, better use for wfm), some ferrite bar, some capacitors, etc.

Case you ned the cable connection information I can provide to you altough I don't have all of them maped.

Low budget helping hand PCB stand

One little and simple "project"

The photo speaks for itself...
The design could be improved but more than 15 years of electronics soldering without "helping hands" there's no point for now :)

The "hand" come from some design store and was really cheap.

Grig

After making the pc programing interface for the TH-F7E I remembered to test against Linux in my Feodra Core 6 box before upgrading to FC10. I remember having tested the USB to Serial cable and not working with my TM-D700 in TNC mode.

Connected the cable to the Kenwood and to the USB plug an called "grig".... nothing.... tested again but powering on the radio after the usb cable, voila.... the bloody thing works... here is the command line "grig -m 220 -r /dev/ttyUSB0 -d 2"

"-m 220" is for model 220 wich is the Kenwood TH-F77, you can list like this:

"....[root@work2 ~]# grig -l | grep -i th

***MEMORY-WARNING***: grig[26426]: GSlice: g_thread_init() must be called before all other GLib functions; memory corruption due to late invocation of g_thread_init() has been detected; this program is likely to crash, leak or unexpectedly abort soon...
217 Kenwood TH-D7A 0.2 Alpha
220 Kenwood TH-F7E 0.2 Alpha
223 Kenwood TH-G71 0.2 Beta ..."

"/dev/ttyUSB0" is the interface created when connecting the usb to serial cable.

"-d 2" is debug level and my version is "grig 0.7.2"

At the moment funcionality is basic but it works, probably with new version of hamlib it could make something else.

My idea was to put the TH-F7 as an scanner connected to the computer to receive some unatended digital modes but I forgot the the audio ouput is used when connected to the computer.... dam!!!

PC programming cable for Kenwood TH-F7E

No big magic here, copy the schematic from the net, make an nice _expensive_ box and "voila": an programing cable for my TH-F7E.
Components were from the junk box and some from my local suplier, I think total cost even from an expensive supplier would be around 10 Eur/USD top most. Cost from Ken-timber(wood) is around 62 Eur, software is free of charge which is nice!

By the way the box is from "Vimeiro" spkarkling water. I have an antenna pre-amplifier inside another water botle in the roof :)
The plugs have to be grinded (trimed) to fit ( full entering) in the radio.



The board was from an power supply experimenting and as always a mix of "Manhattan style" and "Dead bug" which one is faster...

The interface schematic comes from: http://www.geocities.com/azkoza/projects/pg4p/g71cable.html

Here it is the schematic from the above site:












Incidently today as of writing I found another schematic that I didn't tested and dependes on an max232 to make level convertions. Is here: http://www.g1ivg.com/ken_thf7e.htm

Only had an small problem but was on the software side, winblows creates "com port 10" and I was expecting 3 so no communication at the begining.

About the radio: so far so good, easy to learn, a little deaf with the stock antenna ( read: dummy load), no small step on 446Mhz to listen exactly on PMR frequency.

In Linux I still haven't tested the interface because the USB to serial cable is not fully operational, I will upgrade soon to Fedora Core 10 and test then, in FC4 and 6 it didn't worked, I have reception but no transmit. Chipset for the cable is PL2303.

What's up

Busy busy busy.... but still some time to solder...

Pretty much I've been doing some small things:

- Aircraft band receiver (done but partiatly working)
From: http://py2ohh.qrp-br.net/trx/corujinhavhf/corujinhavhf.htm

- Kenwood TH-F7E programing interface (done and working)
From: http://www.geocities.com/azkoza/projects/pg4p/g71cable.html

- Frequency counter from an Chinese store radio (done/broke, done another broke another by static)
From: Chinese store ( also similar do Pound Shop Radio )

- FM receiver (done, working in box but no power is connected to :)
From: An kit laying around in the shack :)

- Loop antenna for MW/SW (done, works, could be improved)
From: Mixed design from web and some experimenting (read: from parts laying around an UTP cable)

- New box for the PSK interface (done, lost 2 screws from the 4 that close the box)
From: Old telecom box

Will post some photos and articles as soon as I find the cable to transfer the images from the camera :)

Other interesting things:

My oscilloscope broke, "caboom", crashed, exploded... I'm trying to fix the bloody thing...
Well it's an advantage, now I have to test things with other methods and learn something new :)

My HF antenna ( some people disagree on what that object is ) broke; well it was make to broke at some point in time, it's just an piece of wire in dipole shape more or less cut'd to the 17m band, hanging on shoe strings between to chemnis pointed est/west... But permit's me to make some nice qso's with only 100w geting over some of those killowat pileup busters that make more electromagnetic noise than an microwave oven! ( you know who I am talking about :)