I have been told by The Mission Trail Net that my 75M signal has never been better – and quite a few people said “Are you in my driveway, what did you do?” . .
I tuned the Mod Bob manually this past weekend on 75M, which is a band that my Elecraft KAT-500 could tune but where the KPA-500 only tolerated about 200 watts before it faulted. That was a clear sign that an L style latching tuner in the shack could not handle the load. I am sure that a Palstar AT2K tuner in the shack would have handled it – but I believe having a 60′ run of coax from the tuner to the antenna with a 1:1 current choke incurred some very serious losses.
The Palstar BT1500A is absolutely the perfect tuner for the KY6R Mod Bob
The design of the Palstar BT1500A is very unique, and fits the bill perfectly. Having the 1:1 balun (current choke) at the input where the unbalanced coax is then turned into a balanced input to the tuner is the first big deal. The second big deal is that the Mod Bob feed resembles an open wire feed, and the impedance varies depending on band. The fact that the BT1500A lets me switch the shunt capacitor at the input or output of what is essentially a Pi circuit adds amazing flexibility, but as I mentioned a few posts ago, this is the circuit that I use for 160, 80 and 30M:
I was lazy before and either used a Palstar AT2K in the shack with my trusty old ACOM 1500, and the KAT-500 with my trusty old KPA-500, but when I stepped my game up to the SPE 1.3K FA, and have found that its not quite as forgiving as the ACOM 1500 was, but the KPA-500 was also not as forgiving as the ACOM. That’s something you will need to understand when you switch from a tube amp to a solid state amp. You can’r be as “lazy” with your antennas because solid state amplifiers with ATU’s should NOT be used with external tuners unless you disengage the internal ATU.
In fact, my new “mantra” is to make all antennas resonant – they will have less loss and better transfer of signal, but with the caveat that they aren’t rediculously shortened – like trying to use a 41 foot vertical on 160M with a tuner. At least the Cushcraft MA-160V was top loaded, so if you have to go small – do something along those lines.
I’m enjoying having an antenna that is resonant on 160M but using it on 80 and 30M with the Palstar BT1500A. I feel like I am doing right by my SPE amplifier as well – which is the reason I went to this effort – which on air – is paying off bigly.