PA3GMP/ZS6TMV ham pages

To me the best part of ham radio is building my own gear, and converting old equipment for amateur use. I get my kicks out of making contacts with simple equipment.
And of course it's fascinating to dial across the shortwave bands and hear some faint, far away radio station through the noise and the fading, from God knows how many thousands of miles away. I remember sitting in the dark one winter evening with a small portable Sony world receiver, listening to the Solomon Islands Broadcasting Company coming loud and crystal-clear out of the speaker.
Unfortunately I have little time for building and even less to make my projects available on these web pages. So this is still a little rudimentary. Bear with me. I'll get around to it one of these days... HI.

The Bosch KF161

The Bosch KF161 is a mobile radio that can be easily converted to the 2 meter band. The design dates back from the early 70's as far as I know, and the receiver could be more sensitive. Also, the noise gate that drives the squelch leaves something to be desired. Still it's a very sturdy radio that you can usually get for a song.
The KF161 uses a PLL synthesizer that reads two divider bytes from a ROM. The ROM holds up to ten dividers, e.g. ten channels, which are selected by the ten-position selector switch on the front panel. This limits the radio to 10 channels.

Converting the set to amateur use involves re-tuning it for use in the 144-146 MHz band, and you will probably want more than 10 channels. This can be done by supplying a range of suitable divider bytes to the corresponding pins at the ROM socket. There are a few conversion kits available from amateurs that do just that, usually by addressing a 2764 EPROM with thumb switches or combining two of the front panel switches with the 10-position dial (so you get 40 channels).
After trying a few of these kits, I decided to design my own. It had to be a completely digital, 'clean' design (read: no R/C networks to introduce dubious pulse delay times), with only one ribbon cable between the main board the display unit. I wanted a rotating enoder for channel selection, with no programmable logic except for a single EPROM to hold channel and display data.
Here are a few pictures of the early prototype.

Mainboard.	Control board.
Mainboard connected to KF161.	Modified front panel.

The Condor 16 and 46

If one radio is good, more is always better. :-) I also have a Condor 16 and a Condor 46. The Condor was developed by Ascom for PTT Telecom in the Netherlands in the early 1980s. Both models look identical. The Condor 16 is the VHF model, the Condor 46 is for UHF. Both models can be equipped with CTCSS and 5TVO tone locks, and they put out about 10 Watts (the 46 can be made to put out a little more, the 16 generally feels happier with just a little bit less). I tend to reduce the output power just a little, so that the finals aren't working at full load and a mistake (i.e. disconnected or bad antenna cables) won't immediately blow out one or more transistors. And two or three watts don't make all that much difference

Converting these radios to the 2 meter and 70 cm amateur bands is not too complicated, and I haven't really made a project out of it. Conversion manuals can be found on various websites, and the pages of Jaap PA3EKI are a good starting point.

The Sommerkamp FRG-7

I first used the Yaesu "Frog 7" when I was working as a trainee at the Delft Polytechnics University in the nineteen eighties, where it was being used to receive telemetry signals from wave measuring buoys in the 27Mhz band. I liked it because it was much easier to use than the heavy and horribly expensive RCA receiver we had as well, and it outperformed the RCA in many applications. We even used it as a broacast receiver. OK, the FRG-7 is still a bit of a boat anchor by modern standards, but it's rugged without being too heavy to handle easily.
A few years ago I saw one at a ham radio auction and bought it for a song. It's not a Yaesu FRG-7, it's a Sommerkamp FRG-7. Yeah right. The brand decal is the only difference.
Unfortunately the receiver didn't work. I opened it up and discovered that some thick-fingered idiot had tried to re-tune it, apparently using a steel screwdriver and brute force. Most of the ferrite cores on the RF board were broken, and the ones still intact were grossly misaligned.
I managed to salvage all the broken ferrite cores but one. I replaced the final one with a core I had lying around. I had to do some experimenting to find the right ferrite (not all ferrites are created equal) and I went through quite a few before I found one that give me the right Q. One run through the entire alignment procedure later, the receiver performed like new. It's accurate, sensitive, easy to use and a pleasure to listen to. OK, you need three hands to operate it, and it takes one switch and three knobs to switch bands, but that's never bothered me. Also it's not as selective and sensitive as a modern receiver with a GaAs-FET front end and a DSP unit, but on the other hand I can service this box with a screw driver and a soldering iron, so it's bound to be around in my shack until the sky falls down.
The most intersting thing about the FRG-7 is its design principle. Instead of a PLL, it uses a Wadley loop, a rather clever method to mix harmonics from a fixed-frequency Xtal oscillator with the incoming signal and the local oscillator, thereby achieving the Xtal frequency stability of a PLL, without actually using a PLL!
More info on the FRG-7 (including the manual and schematics) can be found at Kent Walker's FRG-7 page.

The Yaesu FT-100 Undocumented

If you own a Yaesu FT-100, like I do, you will have realized that the manual doesn't cover everything. There are countless tips and tricks, necessary modifications (!) and service menu settings that you need to get the radio to work properly at all times.
I have compiled a number of these undocumented features into a single document. Most of these are available on the web somewhere, but I've lost track of what came from where so I can't give proper credit to everyone. You can download "The Yaesu FT-100 Undocumented" for free.

The Yaesu FT-100 Documented

Just for my own convenience I like to have the user manual (the official one, supplied by Yaesu) for my FT-100 available online, so that I can always get to it when I need it. So I keep it here.

The Kenwood TH-F7E

My other commercial radio is a Kenwood handheld, the TH-F7E. This is a very small radio that offers 5 Watts on both 2m and 70cm, two simultaneous receivers, one of which is an all mode full coverage one (100KHz to 1300MHz) in something only slightly larger than a pack of cigarettes. It's positively loaded with features and it can even do 9600bps packet radio. Of course it has its disadvantages, the most important one is a total lack of any front end selectivity whatsoever. But that is to be expected with such a small radio. A good front end requires properly dimensioned coils and capacitors, and you simply can't put a filter like that in so small a box. So the TH-F7E is very sensitive to out-of-band signals and QRM in general. But the radio's versatility more than makes up for that, and switching on the built-in attenuator often helps a lot.

Again I like to have access to the manual for this radio at all times. So just like the one for the FT-100, I keep this one here, plus the documentation for the communication protocol for this radio.

Links I find interesting

PA0FRI

Frits Geerligs PA0FRI has some very interesting ham projects on his web pages, most noticably a few nice tube linears. Partly in Dutch.
URL: www.pa0fri.geerligs.com/

MMhamsoft

Makamoto Mori JE3HHT has created some excellent ham radio software, including MMSSTV and MMTTY. Working digital modes is, especially due to the good DSP routines in Mako's software, very simple indeed.
URL: mmhamsoft.ham-radio.ch/

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