B29. Trio/Kenwood TS-500, TR-7010
This is probably the worst receiver I've ever
had in my home, but it was soon discovered that it was very
to improve it, in fact only addition of a 22kW resistor in the AGC detector circuit. Copied the idea from Drake 2-B,
and the result was inbelievable good. Tried later to improve it further using a 2N4401 like the AGC detector in 2-C,
but it wouldn't really improve. You could achieve 1dB variation in audio signal with RF level varying between 0.5µV-1V,
but it is no point, in fact it is not an advantage in making the speech intelligible, 6dB seems optimum, so the first
suggestion was just optimum. TS-500 has moderate IF output level and it needs no AGC-amplification.
In Drake receivers the IF output levels are low, say 4-10Vpp, and an extra IF amplifier is required,
6BJ8 or 6BF6 in 1-A, 2-A, 2-B, and 2N3877=2N4401 in 2-C, and the R-4 series. 6BF6 is a special valve,
and you cannot use the low current 6AT6, 6AV6, EBC90, EBC91 audio amplifier types.
A very much same circuit is ALC improvement for FL-DX-500 while the modification there is
addition of a 3300 ohm resistor in series with the time-constant capacitor.
The addition of 33k resistor in series with the 0.1µF capacitor is an incredible improvement to
the receiver audio sound. Later used 1N4148 diodes and added a 1MW resistor. M is RX-mute-line,
grounded for receiver, open relay contact for transmission
But the next
versions of the TS-5xx transceivers were not much to write home
here is the good/bad story of the next model (Signal intelligibility)
LA4O club should operate LA1X at an exhibition in Oslo in 68. We had got the latest Japanese rubbish
on the marked, but nobody cared to approach the stand. It was an obvious demonstration of operation for
certain strange persons and the public avoided us. So Gudmund, LA2DL understood that something was
going really wrong. He got home and collected his own Drake TR-4 rig and later installed it at the stand.
And just as we had removed the Japanese junk and installed the Drake rig, the stand caught considerable
interest, now the public suddenly understood that what was going on on amateur bands was conversations
which everybody could cope with. LA2DL's initiative was important and after this I was even more
critical to improper designed rigs. Still sometimes I hear somebody comment that
"don't know about the receiver, but the transmitter is good". So, for a period I accepted only Drake equipment
for the good intelligibility from the receiver sound, got the 2-B in december 68, TR-4 in 74, and R-4C in 76,
and another 2-B in 77, but some Japanese equipment has been useful, and I've also learnt how to improve the
sickness, which is usually caused by improper AGC time constants and in two occasions, improper product
detector, but quite simple modifications - when you learnt what was to remove or add. Have therefore
kept FL-dx-500 since 74, TR-7010 since 76, FT-7 since 82, FT-902 since 88, IC202 since 85.
Trio/Kenwood TR-7010 2m
ssb/cw mobile transceiver
Got my rig in 1976, and used very much time trying to cure the very bad audio quality. Improved the AGC
a lot, but it was later discovered that the main problem was the product detector. Two capacitors and a
resistor was removed and the performance was incredibly improved
The VFO covers 8200-9200kHz and seems to be made for TR-8200, but I used mine for TR-7010
2m SSB/CW mobile transceiver to cover 144-145MHz band. For this purpose only the VFO was needed.