[Elecraft] You probably do not need a K4HD for SO2R contesting

[Jim Brown]

Bob is a top contester, often operates from top contesting stations, and 
I strongly value his comments. I'm not far from Bob, or W6NL and K6TD's 
remote (both mountaintop stations, line of sight). Last I heard, W6NL is 
running Yaesu rigs, lots of phase noise and clicks; I don't know what 
K6TD is running, but I suspect Flex. W0YK and K6XX are very close by, 
both mountaintops. K6XX is VERY clean, only five miles N. We can work 
500 Hz apart on CW, both running legal limit. YK and XX are also running 
K4s; I'm runing K3s with updated synth boards.

73, Jim K9YC

On 1/27/2021 12:56 AM, Bob Wilson, N6TV wrote:
> Old Subject line was:  "K4 Panadapter Display"
> 
> This is in response to the post by NJ8M, excerpted below.
> 
> I've been testing a pair of K4D (not HD) radios for SO2R (Single Op Two
> Radio) contesting at my QTH, which has one tower, closely-spaced monoband
> antennas, and 1500W output.  I'm using Array Solutions 200W W3NQN Bandpass
> filters and Top Ten Devices coax stubs.  There are two or more contest
> stations on the mountains above me (K6TD's remote, and W6NL) that are
> line-of-sight, and they can produce very loud signals, S9 +50 dB or more
> off the back of my beams.
> 
> The front end of the K4D performs just as well, as far as I can tell, as
> the two K3 radios I used before, which had 8 pole crystal filters (the
> Inrad 500 Hz 8-pole crystal was my favorite).  I've heard no "AGC pumping"
> or "desense" on the K4D, from either of these loud stations a few kHz away,
> though I can hear their transmitted phase noise, and see it on the K4
> scope.  I can transmit on one band and listen on an adjacent band, and
> though I hear my harmonics or IMD for neighborhood non-linear devices in
> certain directions, the K4D receiver doesn't "block" when I transmit on the
> other.
> 
> As I've mentioned before, the K4D audio is a vast improvement over the K3
> and K3S, which really helps when you're lucky enough to attract a pileup.
> The QSK is better too, which helps when you're calling in a pileup.
> 
> Furthermore, you DO NOT need to tap multiple times to switch to the RX
> antenna, as seen in the recent live demo by WA6HHQ.  What Eric did not get
> to demonstrate is that there is an ANT CFG menu option that allows you to
> select which antennas you want the RX ANT button to cycle through.  When
> that option is selected, a single tap of the RX ANT button toggles the
> receiver between the TX ANT and RX1 antennas, say, instead of popping up a
> menu, so the K4D can work the same as the K3.  You can also toggle an RX
> ANT in and out from the keyboard of your logging software, simply by
> sending a host command with a function key. Or you can cycle through
> multiple RX antennas with each tap.  The same applies to the TX antennas.
> 
> The 8 K-POD buttons can also be used to send host commands (or "macros") to
> do anything you can do with a button, or several buttons.
> 
> The only time the K4HD model might be best would be when there are two rigs *on
> the same band*, such as at Field Day, or at a large DXpedition, or at a
> large Multi-Multi station with a RUN and MULT stations on the same band.
> 
> And, as I understand it, the plan is that a K4D can be field upgradable to
> an K4HD model at a later date.  What remains to be seen, though, is if the
> "ripple" in the roofing filters of the HD module introduces any pileup
> mush, which was one explanation for why the K3 and K3S still had some
> pileup mush, even after the K3 AGC settings and RF Gain were properly
> adjusted as recommended here
> <http://elecraft.365791.n2.nabble.com/K3-Receiver-mush-tp7627277p7627323.html>.
> Time will tell.  As of now, I haven't heard any pileup mush (RX IMD or
> Audio IMD) in the K4D.
> 
> As for noise blanking and noise reduction, it's not something I can offer
> an opinion about, because I prefer to leave both OFF, as I did on my K3.
> 
> 73,
> Bob, N6TV
> K4 Field Tester
> 
> On Tue, Jan 26, 2021 at 9:15 AM Morgan Bailey <mbaileycrna at gmail.com> wrote:
> <snip>
> 
>> For me I need a bomb proof front end for a high RF environment, namely
>> SO2R on a city lot using the same antenna for 2 radios at the same time
>> with band pass filters and multiplexers that offer 100db of rejection. To
>> date no SDR only radio offers what a superhet offers. Until the HD model is
>> implemented, the K4 is not the radio for me.  If I were to be a one radio
>> shack radio user and not 2 for SO2R, it would be my first choice. For
>> instance, the IC7300 and IC7610, both are fantastic radios. Put another RF
>> source remotely near them and the ADC is overloaded and the AGC
>> pumps/attacks and you hear nothing. Both are a massive failure when using
>> SO2R or at Field Day. The second thing that I need, being in a large city
>> is the ability of the receiver to deal with intermittent noise problems.
>> Line noise and the increased noise floor that highly populated areas hit
>> the front end of a receiver has to be ameliorated by the receiver.
>> Algorithms for noise blanking, and digital noise reduction and a tunable
>> passband capability without ringing and loss of weak signal detection is
>> what is needed. That is a tall order. Narrowing down the frequency by a
>> superhet front end and adding band pass filters to help with this will cut
>> the work of the ADC down due to the decreased spectrum that needs to be
>> converted. Then the FPGA and DSP sections do not have to process so much
>> data and this should speed up the response time and will add increased
>> selectivity, hopefully.  But until the HD is implemented this is not going
>> to happen.
>>
> <snip>
> 
>> Morgan Bailey NJ8M
>>
>>
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