Thursday, June 07, 2007

Realistic HTX-100

The 30th Annual Conference of the Central States VHF Society was held July 26-28, 1996 at the Thunderbird Hotel & Convention Center in Bloomington, Minnesota. Among the papers presented was Make Your HTX-100 a Flexible IF Transceiver by Rus Healy, NJ2L (now K2UA).


Anonymous said...

In Rus's excellent instructions one paragraph confused me:

3) Locate C74, a 560-pF ceramic disc capacitor, near the right-rear corner of the radio's main PC board. This is the interstage coupling capacitor, and it's a good place to pick off about 40 mW (+16 dBm) of transmitter power. Lift C74 from the circuit. At its output side (after Q501), on the trace side of the PC board, solder the center conductor of a piece of small coax, such as RG-188 or RG-174. This leaves the capacitor in the circuit, which provides dc blocking for the low-level output. Solder the coax shield to the PC board ground foil nearby.

I stared at the board and reread the instructions, wondering how I could follow them...

If I lifted one lead of C74 and connected the center conductor to it, I wouldn't be on the trace side of the board and I'd have no ground foil nearby.
If I lifted one lead of C74 and connected the center conductor to the vacated pad on the trace side, C74 would be left out of the circuit.
If I left C74 in place and connected the center conductor to its pad, the capacitor wouldn't be lifted.
Also, C74 runs between Q501 and L25. It has no direct connection to ground.

[posted by: scott]

Anonymous said...

I emailed Rus for help. Here's most of his reply...

What happens when you follow my description in the article is that the capacitor remains in the circuit, but you move its output side from where it was--the input to the next stage--over to a piece of small coax that you can bring out the back of the radio to connect to the transverter.

The connection between the capacitor and the coax center conductor is up off the board, "flying lead" style. You need to make sure to strain-relieve the small coax so that it can't rip the capacitor off the board if it's stressed.

Does this help?

Good luck with the transverter. It's that time of year . . . [posted by: scott]

Anonymous said...

...I suspect my transverter took a hit during yesterday's violent thunderstorm. The thing hadn't been connected to an antenna for 8 years till this week... Murphy?

The June 5 storm centered on Anna for a spell, battering the Honda with hail while she sat there alone in the car.

Mom got her home and they went to rest on the sofa. The storm reached into the house and powered up the Barbie Laptop on her bedroom floor -- 10 feet from my Downeast Microwave Inc 144-28 transverter, its IF HTX-100, and an outdoor wire.

The next listen on the pair yielded no signals. I had been able to hear (unintelligible) FM signals on my one listen prior to the strike, but those frequencies are inappropriately silent now.
[posted by: scott]