#41 Shop Talk Projects, Past, Present, and future

[Radio Tech]

In this video we have a look at a few projects that are in process and future projects that will be coming soon.

Hamtronics repeater
Regency repeater
VHF homebrew duplexer
Heathkit HW101
National NCX-3
Siltronix 1011C





Link to Hamtronics R76, T51, CWID, COR repeater boards:
http://gokarters.com/smf/index.php?topic=2555.0

[German_EE]

Oh man, you are sure going to be busy until at least Christmas.

That repeater brought back some happy memories. About 35 years ago I helped construct a 2m repeater for our local ham radio club, at the time I had a brother who was in the Army and we used ten 'surplus' 150mm inch shell casings to make the diplexers (he was in the artillery). They were solid brass, perfectly machined and very heavy but just the right size. So far as I know those diplexers are still in use although I'm sure that the electronics will have changed by now.

P.S. A quick tip, lose the wave.

[AF6LJ]

The good thing about the Siltronix is you have to add a power supply for the DDS VFO. As you may or may not know... The internal VFO runs off -10V which is derived from a very power hungry voltage divider off the -100V bias source. (I worked on a 1011B once) For those who are interested the Siltronix 1011s are based (mostly) on the Swan 270.

Here is what I would do given a chance...
1. install a split DC supply make the negative side -10V for the carrier oscillator.
2. get rid of those resistors used to drop the bias voltage down to feed the Zener that regulates the -10V and get rid of the Zener.
The radio will run cooler.
3. Re-tune the radio for 10 meter operation only.

[Radio Tech]

Oh man, you are sure going to be busy until at least Christmas.

That repeater brought back some happy memories. About 35 years ago I helped construct a 2m repeater for our local ham radio club, at the time I had a brother who was in the Army and we used ten 'surplus' 150mm inch shell casings to make the diplexers (he was in the artillery). They were solid brass, perfectly machined and very heavy but just the right size. So far as I know those diplexers are still in use although I'm sure that the electronics will have changed by now.

P.S. A quick tip, lose the wave.

Yes lots to do here. Always busy.
Shell casings should had worked great. Wish I could find some of those. That is using your head.  Been looking for some copper tubing but no luck yet.  But been out of town all week and just got back in. Was too tied to go out hunting for stuff today.
 Yep, agree about the wave. Was a bit corny but did not have time to reshoot the beginning.
Thanks.

[Radio Tech]

The good thing about the Siltronix is you have to add a power supply for the DDS VFO. As you may or may not know... The internal VFO runs off -10V which is derived from a very power hungry voltage divider off the -100V bias source. (I worked on a 1011B once) For those who are interested the Siltronix 1011s are based (mostly) on the Swan 270.

Here is what I would do given a chance...
1. install a split DC supply make the negative side -10V for the carrier oscillator.
2. get rid of those resistors used to drop the bias voltage down to feed the Zener that regulates the -10V and get rid of the Zener.
The radio will run cooler.
3. Re-tune the radio for 10 meter operation only.

Sue. That is great information. I had already looked at supply voltages and figured I was going to have to install a separate supply to run the new circuit. Thanks very much for confirming all that.   

[AF6LJ]

Oh man, you are sure going to be busy until at least Christmas.

That repeater brought back some happy memories. About 35 years ago I helped construct a 2m repeater for our local ham radio club, at the time I had a brother who was in the Army and we used ten 'surplus' 150mm inch shell casings to make the diplexers (he was in the artillery). They were solid brass, perfectly machined and very heavy but just the right size. So far as I know those diplexers are still in use although I'm sure that the electronics will have changed by now.

P.S. A quick tip, lose the wave.

Yes lots to do here. Always busy.
Shell casings should had worked great. Wish I could find some of those. That is using your head.  Been looking for some copper tubing but no luck yet.  But been out of town all week and just got back in. Was too tied to go out hunting for stuff today.
 Yep, agree about the wave. Was a bit corny but did not have time to reshoot the beginning.
Thanks.

Somewhere in the old Ham Radio magazine issues is an article on douplexers.
Turns out most of the bandpass / bandreject douplexers are built around a 73 ohm transmission line. (the internal spacing between the tuning stub and the outer housing) There is also some kind of relationship between the lenght and the diameter of the inner wall of the cavity.

[SeanB]

Replacement for shell casings is to go to the local plumbing wholesalers and get a few copper solder on end stops for 4 inch copper water pipe ( note there is a sticker shock associated with these fittings) and a short offcut of the 4in pipe. Then you simply silver solder the end stop to the pipe after getting the lengths right, and put the couplers in there. If you can get bigger pipe use it.

Still cheaper than a bespoke cavity filter though.