[Elecraft] K4

[Victor Rosenthal 4X6GP]

I am line-of-sight to a 50kW AM transmitter (at least one, maybe more 
co-located at the site). I was using a vertical antenna, which was very 
good at picking up AM BC signals.

I had a problem that the plentiful RF overrode the bias on my K3's T/R 
switch diodes, causing IMD all over the lower bands. I made a HP filter 
that cut off at about 2 MHz (I don't operate on 160m) and that cleaned 
it up.

When I switched to a horizontal antenna, the problem went away. Now in 
addition, I am using a Johnson Matchbox, which is very good at 
attenuating out-of-band signals.

If you have a similar problem and you make a HP filter, note that it has 
to have power-handling capability so you can transmit through it. The 
t/r switch and the K3 (and probably in the K4) is before the alternate 
RX input/output, so you can't just put the filter in the receive path.

As someone else pointed out, none of this applies if the IM is being 
generated by chain-link fences or any other non-linear junctions out there.

73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 19/04/2020 22:31, RALPH TURK wrote:
> Wayne et all
> My only concern before I order a K4 is how it will work with two high power
> AM transmitters near me.
> 10KW day,1kw night  KVOI south of me and a 50kw day only KUAT AM north of me.
> At some time, I will need to borrow or rent a k4 for a week and see how it behaves
> The majority of my operation is between 2-3.5 Mhz, 4 to 7mhz,  7.3-10mhz, 11mhz to14mhz.
> I also use my radio on most ham bands.  I currently use a K3 with all bells and 1000MP
> The MP seems to handle the intermod better then the k3
> The intermod is not caused within the radios but cause by rusty chainlink fence, poor power line
> grounds etc.  My antennas are not the problem.  I tried a sharp cutoff filter for everything below
> 3.5mhz.  No positive measurable results.
> 
> Ralph, W7HSG, AFA9RT
> 520-444-6610