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Matt Thomas, W1MST, is the managing editor of AmateurRadio.com. Contact him at [email protected].

As I suspected the microphone amplifier Q1 in the Kenwood/Trio TR9500 was indeed faulty. The replacement arrived next day and within an hour I had successfully soldered in the new 2SC2240 transistor and it now had audio on transmit.

Transmitting into a dummy load and monitoring on my FT857-D the FM transmission was fine, the SSB was okay, perhaps slightly over driven. I suspected that maybe the previous owner might have twiddled something to compensate for a failing Q1.


In the adjustments section of the service manual VR6 on the IF unit controls the SSB MIC gain. To check the settings it was a case of setting the transmitter to 432MHz and putting an audio frequency signals of 1.5kHz of amplitude 1mV and 10mV from my signal generator on to the microphone terminal, and observing the RF power output, which were the 5W and just over 10W as required. As this didn't need altering I left it alone and boxed it back up and returned it to the happy owner.

Last night was the RSGB 432MHz UKAC Contest and I was hoping to here it on the air, sadly I didn't. It now transpires that there maybe another issue with it, something I should have spotted.

I do remember something strange when doing the initial testing. Connected to a dummy load and in SSB mode the S-meter showed S9+ when in receive but with no audio, turning the RF gain control the meter dropped to S0 and normal white noise static could be heard. It received a SSB transmission from the FT857-D with no issue so I thought no more of it. Being over eager and not experienced with using different rigs I had mistakenly dismissed it and should really have read the operating manual more extensively.

The anomalous S9+ meter reading and no audio occured when the RF gain control was set to the maximum which is the normal recommended setting for operating, I'd simply turned the RF gain control to the minimum mitigating the issue.

Obviously the rigs owner had put the RF gain back to maximum and was now reporting it wasn't switching back to receive. In fact it is but nothing is being heard. Checking the service manual this morning and it appears there is an issue with the AGC circuit (description and block diagram below)

RECEIVER CIRCUIT
.... The signal is picked up from the last stage of the IF amplifier (Q23), then detected and amplified to generate the AGC voltage. The AGC time constant is automatically set according to the mode : FAST for CW; SLOW for SSB. The AGC voltage is applied to IF amplifiers Q21, Q22 and Q23 (3SK73(GR)) and RF amplifier Q51. It is also used to drive the S meter.

It seems the rig may well find itself back on the bench, however this repair could be more problematic!

As I mentioned it was the 432MHz UKAC last night and I had a decent night of search and pounce. Conditions were very strange, lots of fading and strangely some of the usual local operators were not heard. I was very pleased to catch some lift and made a couple of decent DX contacts in Northern Ireland, The Isle of Man, Northumberland as well as Essex and Cambridge.

Who needs a preamp on 432MHz with ears as good as mine? Well actually I do desperately! #ukac pic.twitter.com/WXnMBGY0uw
— Andrew Garratt (@nerdsville) September 9, 2014

In a few weekends it is the National Hamfest, which is held in my home town and I hoping to pick up some bargain gear to improve my UHF set up, however from past experience that may prove difficult.
Andrew Garratt, MØNRD, is a regular contributor to AmateurRadio.com and writes from East Midlands, England. Contact him at [email protected].

It's been over a month since my last post. The day job, busy weekends and yes even a little radio have kept me occupied. I won't bore you with the non radio stuff, but I'll try to hit the highlights of the last few weeks.

SOTA

I've been on a couple of SOTA excursions. The first was mid-August to the Davis Mountains in West Texas. If you have never been there, it is an oasis in the middle of a desert. With mountain elevations in the 6 -7,000 ft. ASL, the climate is much closer to a summer alpine climate than a desert climate. Afternoon showers keep the entire area lush and green. I partnered with Mike,  KD5KC on this trip and did three summits, Pine Peak W5T/DW-003, Summit 6641, W5T/DW-018 and Locke Mount, W5T/DE-003. Locke Mount is the home of the McDonald Observatory.

Pine Peak was a first activation for that summit. It is located within the Nature Conservancy boundary, It is open to the public a couple of weekends a year, so we made sure to be there that weekend. It is a pure bushwhack with no trails to the top, so we had fun making a path.


Mike Crownover, AD5A, is a regular contributor to AmateurRadio.com and writes from Texas, USA. Contact him at [email protected].

Courtesy: https://www.google.ca/maps/

Propagation to Alaska was much better than usual this morning. A two-minute Perseus recording at 1300z, about 45 minutes before my local dawn, revealed some excellent signals. Unlike many of the beacons in northern Canada, most of the Alaskan NDBs are not purposed for long-range use and run the standard 25 watts into 'T' or short loaded vertical antennas located right near the runway.

09/09/14 1300 529 SQM Level Island AK CO36

Highlighting the morning was my first "new catch" from Alaska in several years - 'SMA' at St. Mary's Lake on 230kHz. It has been on my morning check list for many many years but only today did it decide to reveal itself!

09/09/14 1300 230 SMA St. Mary's AK AP82 USB 231.085 no sign of a LSB

Reported to be running 70 watts, this particular beacon has never been reported to the RNA NDB list nor even heard by those listening in Alaska. I suspect either a very tough path or a system in need of a tune- up. A Google Map view appears to show a single vertical antenna but it may be one end of a 'T' support.

Courtesy: https://www.google.ca/maps/

Hopefully conditions will continue to improve as there are still a few up there that have yet to be logged!
Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].

Drain (top) vs Gate (lower) on testbed Class-E GW3UEP TX

I've just completed the Muppet-styled printed circuit version of my previously breadboarded GW3UEP 630m transmitter. The earlier version was built "ugly style" in order to optimize part values and measure circuit parameters.

Testbed (Ugly-Style)

The "ugly version" performed well at 12V and during overnight beacon testing was aurally copied as far east as Kansas. Although the final version has yet to be mounted on its small 19" rack panel, along with a meter to monitor final amplifier drain current, all indications show that it too works well.

Final Version (Muppet-Style)

This version, based on the GW3UEP design, has a few small changes, the main one being the addition of a second parallel-connected FET ....described in an earlier blog.

Running the TX at 12.8VDC on the drain(s) at 2.3A produces an input power of 29W. The measured power out, after the LPF, is 23W into a 50 ohm load. This represents an efficiency of 80%. When run in the normal speed CW mode, the FETs run cool enough that they would probably not even need a heatsink but if run in any of the QRSS (long keydown periods) modes, would certainly benefit from  heatsinking.

Running the TX at a higher voltage of 22.6VDC (on the amplifier only) yields a current of 4A for an input of 90W. Measured output power is 71W for an efficiency of 79%.

Heatsinking would be required at this power level, even for normal speed CW but the finals seem to run just slightly warm. A larger heatsink or possibly a small fan as well would be required for any QRSS CW modes.

I suspect that the efficiency could be further improved yet with very fine tweaking of the output circuit L/C network but the extra few watts gained would not be significant.

At either power level, this easy-to-build transmitter would make a great "first 630m transmitter" for anyone wanting to get started on our new band.

Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].

Series Seven Episode Eighteen of the ICQ Amateur / Ham Radio Podcast has been released. The latest news, Martin (M1MRB & W9ICQ) and Colin (M6BOY) the history of Amateur Radio Exam passes and Martin (M1MRB & W9ICQ) interviews Bill Meara N2CQR.

• Sotabeam End Fed Tuner Kit
• Schedule for RSGB Convention released
• The first Greek microsatellite is a fact!
• Yaesu FT-991 KW/50/144/430 MHz Transceiver
• Southend & District Amateur Radio Special Event
• New Zealand's Prohibited Equipment Notice updated
• Western Australia gets Summits on the Air
• 90th Anniversary of first UK-NZ contact

Colin Butler, M6BOY, is the host of the ICQ Podcast, a weekly radio show about Amateur Radio. Contact him at [email protected].

Series Seven Episode Eighteen of the ICQ Amateur / Ham Radio Podcast has been released. The latest news, Martin (M1MRB & W9ICQ) and Colin (M6BOY) the history of Amateur Radio Exam passes and Martin (M1MRB & W9ICQ) interviews Bill Meara N2CQR.

• Sotabeam End Fed Tuner Kit
• Schedule for RSGB Convention released
• The first Greek microsatellite is a fact!
• Yaesu FT-991 KW/50/144/430 MHz Transceiver
• Southend & District Amateur Radio Special Event
• New Zealand's Prohibited Equipment Notice updated
• Western Australia gets Summits on the Air
• 90th Anniversary of first UK-NZ contact

Colin Butler, M6BOY, is the host of the ICQ Podcast, a weekly radio show about Amateur Radio. Contact him at [email protected].