Or perhaps there is a unique mixing of the LO in the Transverter with
similar in the K3 to give a result? I have never had anything good
result from running the noise blanker in any radio while involved with
2M MS and EME here. Also usng the K1FO 12 and have APRS as well as
Digital Paging system running a KW about 1 mile away at 144.9 Intermod
can be a crazy thing--especially with mega-FM stations locally.
FWIW
Curt KU8L
On 7/27/2018 10:48 PM, Wayne Burdick wrote:
Another thought: The K3 has two noise blankers. The hardware blanker does see a
broad input frequency range (so it can suppress very fast-rise-time noise
pulses), and as with similar blankers, you have to keep the NB threshold high
enough to not cause intermod.
Try using just the DSP blanker, which is post-crystal-filter. Or a touch of
each. This can be very effective on disparate noise sources.
Wayne
On Jul 27, 2018, at 6:59 PM, Richard Beerman <[email protected]> wrote:
Wonder if anyone else has encountered this on 2 Meters? I am using a 12 ele
K1FO yagi - about q12 dB gain on 2. That enters the shack where it is connected
to a Downeast Microwave 50 Watt transverter with about 17 dB gain on receive.
The output of the transverter is connected to transverter input on my old K-3.
For the longest time, I was receiving loud QRM from what I initially thought
were power line noise bursts. But, I became suspicious because these bursts
were about a second or so in duration consistently. During this time, I was
testing my setup for meteor scatter using the MSK 144 software found in the
current WSJT-X suite. These loud bursts created huge red images on the monitor
watching in 144.150 MHz, the MSK144 calling frequency.
I got suspicious that these signals were not simple electrical pole shorting
noise. So, I connected a whip to my old TS-790S rig and tuned it to 144.390
MHz, the North American APRS frequency. WALAAAAA, the signals on my monitor
connected to a K-3 tuned to 144.150 MHz corresponded perfectly to the WPRS
signals on 144.390 MHz, some 240 kHz away! The preamp on the K-3 was off. There
were no other receiving preamps in line at the time. Later, I turned on an
external 2 Meter preamp and all that happened was that the APRS signals were
larger at 144.150 MHz.
It appears that the front end of my K-3 simply folds up in the presence of
strong signals that are WAY off the receiving frequency. I can tell you that
connecting the same antenna/transverter to a Kenwood TS 590SG, there were no
traces of the APRS signals. And connecting the TS-790S to the K1FO likewise
produced no APRS QRM at 144.150. To me, with the presence of a number of strong
APRS signals on 144.390 makes this K-3 extremely unusable on 2 Meters. I was
running the K-3 noise blanker to handle the rest of the noise here but
likewise, I also had noise blankers running on the two Kenwood radios as well.
Any suggestions are welcome. Dick W5AK
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