Homebrew Transverter for 40, 20, 15 and 10 meter bands

 Homebrew Transverter for 40, 20, 15 and 10 meter bandsd

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I stumbled upon this fragment from my old geocities (now that should give you and idea of how dated this article is) page and thought I would post it here.

"Homebrew Transverter for 40, 20, 15 and 10 meter bands

and other Trivia

By Ramon R. Reyes, DU1FV

You must understand I was desperate. I used to drool over the nice pictures of the Icom IC-730 on the back cover of thje Japanese CQ Ham radio, back then. I simply could not afford a decent HF rig. While browsing another issue of the same magazine, I found a construction article (in Japanese, of course) on a transverter for use with a 2 meter all mode rig designed to work on the 30m band (10 Mhz— part of the WARC bands approved that year).

I had just gotten the “amnesty” papers from the NTC (ay naku binalot ba naman ng masking tape at ni rubber stamp ba naman sa ntc...)for a used 10 watt 6m rig I bought from, of all places, a shoe store in Virra Mall (sinamahan yata ako ni Nas (DU1ON). He probably pointed out the store to me. I had connected the rig to an external antenna, but there was not much activity in that band.

Then it occurred to me: “ why not make an HF transverter for my 6m all mode Icom using the same techniques in the Japanese article?” From that moment on, I became hopeless victim of … Homebrewer’s fever.

I did the math and determined the exact frequency of the crystal required. Armed with a trusty grip dip oscillator, I started winding the coils, and did more research on obtaining that one part in the schematic I was not familiar with —- the “DBM”. So out came the ARRL handbook and all the lit I had been collecting all these years. DBM = double balanced mixer.

Meanwhile, I went to Republic Crystal in Little Baguio and ordered the crystal. I had a chance to meet Earl Hornbostel who turns out to a ham - DU1EA. (now silent key). (The first time I read of his call was in the DU world map centered in Manila ( the map with no VK land, I think) reproduced by PARA. The map mentioned he was one of the mainstays of DU1UP (DX1UP) in Diliman). As a freshman in the UP, I remember wandering through the top floor of the engineering building, stumbling upon some old radio rooms and seeing QSL cards from all over the world on one of the walls. I also recall vividly the remains of the transmiting equipment probably of DZUP, which was damaged during the Diliman Republic days.)

Now Earl was very helpful and had a lot of stories. It turns out that he was very much into contesting during his days. I remember that glint of pride in his eyes when he took me into a back roon and showed me his favorite homebrew project — a two tube linear in push pull configuration. If I recall correctly , the plate transformer looked like it came from a Meralco high voltage distribution transformer. Maybe it could handle 5kw easily! I wonder where that project is now. It may be gone but it sure was an inspiration to me.

Anyway, while standing in the waiting room at Republic, there was this sheet on paper posted on the wall which read “SBL-1 now available”. “SBL-1”? I said to myself, “Teka muna, ito yun part na ginagamit na mixer sa schematic doon sa Japanese magazine article” – a double balanced mixer—the DBM. I had intended all along to use a more familiar and readily available dual gate FET configuration. But here it was right in front of me. Well you could imagine the excitement. I wasted no time in buying one. The schematic called for 2 pcs but I thought I might get away with one if I did some modifications. I was on tight budget.

The TX side was fairly straight forward. It was the RX that was the challenge. The double balanced mixer was a big improvement over the dual gate mixer design that I used for an earlier experiment—a simple cb rig to forty meters transverter. The SBL-1 was simply a “stronger” mixer and was less prone to overload from the night time deluge of signals from broadcast stations just above the forty meter ham band. With the old fet mixer, there was a "hash" when I listen in on the ham frequencies at night. It was nice to actually “hear” the performance of the ring diode DBM as predicted by the ARRL handbook.

Pretty soon, I was on the road to winding the coils for the other bands—20 15 and 10. The chasis had barely enough space for the entire four bands. Construction was dead bug style.

When the project was completed and finally tested, it felt great. I did not have the energy to transform it into a decent etched pcb version for I was more concerned with having the theory put into actual practice. Going on air was a lot fun. In one of the pics, you can just see the DBM with the brass shim wall running "through" it.

In the months to follow, I started to be distracted by computers. There was this person who I met casually in the maternity ward when my second daughter was born. He later turned out to be a ham. He actually stormed into the pediatrician ’s office wanting to know who owned that car parked outside with the call letters "du1fv" on the rear windshield. It was Frank Buck , G3JNO/DU1 who lived in Montalban. After a while we got to talking on the radio and he found it odd that I was not into computers yet. He gave me an old xt motherboard, a floppy disk drive and a power supply. My first pc essentially. I had to hook it up to a tv to see the "c prompt." I soon fashioned a case for the mob from an old steel chassis! That was fun.

Computers was a big “distraction”. Dos 3.1m paket 5– an aussie program, bbs s, 386s Celeron overclocking, client server, sql server, then BAMMM! The INTERNET!

There was a time when it was held that the internet would soon cause the demise of amateur radio.

Well the jury is still out on that one. I have heard of not just one ham selling all off his radios to get the computers and just surf and chat.

In my case it was access to information and equipment sources that has rekindled my interest in homebrewing and rf design in particular and amateur radio in general.

These internet sources include info like device data sheets, online supplier web pages, USENET, other ham forums, ham personal web pages featuring a lot of construction projects. An to top that, these online hams share experiences when contacted by email, etc. A lot of online ham parts stores ship to the Philippines too.

As far as local parts acquisition is concerned, the local electronics district in down town manila is typically now just 35 minutes away by metro rail transit . I usually jump on the train when the part is not available from the nearby Marcos Hi-way DEECO store (a fifteen minute walk away).

As if by magic or mysterious alignment of the planets, there recently occurred a “fortunate series of events” (another long story) that led to revitalized interest in ham radio among the old members of the ham club. This ultimately resulted in the putting up and licensing of our current UHF repeater. May we then dare quote the ol' country cowboy singer Gene Autrey and say “We are back on the saddle again!”."

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16Robert Reyes, Jaycee Crisostomo and 14 others