80M Switched Linear Loaded Vertical

My 60′ (18M) wire vertical for 80M covers about 30 khz at the same SWR. This means I will be good to go in the CW portion of the band (center the “long line” for 3.515), and then cover where the nightly net is (center on the “short line”).

246 divided by the Frequency in MHz = Length in feet

246 / 3.515 = 70′ (5′ up and back down)

246 / 3.857 = 64′ (2′ up and back down)

The ladder line stubs plug in on the top right and left of the box, and the center feed through is for the vertical wire taped to the Spiderbeam 18M (60′) mast:

I can actually just hard wire the coax in shield directly to the radial (gnd). There is no need to bother going through the relay. I’ll keep the leads very short and close to the terminals – which can be bolts – the same that Balun Designs uses since the box is plastic.

With two pieces of ladder line and 3 relays, I can switch between 75 and 80M and be covered perfectly. I didn’t have this issue on 160M, because I was 95% percent of the time between 1.815 and 1.830 – so only 15 khz for almost all DXCC QSO’s.

The best thing about this is there are no coils or capacitors that get hit with very high voltage, and I think this little bit of linear loading (16%) means virtually no sacrifice in performance. The Elecraft gear – especially the KPA-500 will like this. 80M has always been a bit “finicky” with the KAT-500 and the KPA-500 . . .

The default (position 1 on my switch box) does nothing – its not even hooked up, and its the 75M CW band portion, and Position 2 is for 80M, and a voltage is applied. The two relays are wired “opposite” each other – one is NO and the other NC when voltage is applied. This means there is no chance that a path is open where both are switched in. I also do not add the length of one stub to the other.

I will build the relays in a small box and also use a current choke that is always in the circuit. I’ll tune using the Rig Experts AA-30, so this will be pretty easy – a couple hour project. One thing I have learned – it is FAR better to be a little long than too short. Now I really understand why shortened verticals on the low bands lose efficiency as severe as they do – and also understand how you can move the high voltage and current nodes around based on size.

ZS to W6 Pipeline

The year long ZS – W6 pipeline is still going strong. I worked Bill – ZS6CCY where he was S9 +10 and I was S7 with only 100 watts. I never get tired of this – and really enjoy my DX Engineering DV-40-P phased vertical array.

70′ Ladder Line Vertical for 80M

Using ladder line – I can use one side for the 80M CW band (70 – ish feet) and one side for the 75M side (63-ish feet). I have an extensive radial field that proved itself on 160M – earning me DXCC on that band – so now I will come up with something on 80M that avoids any kind of loading – so that I have a true quarter wave vertical on 80M.

The phased vertical idea did not pan out – but I am sure that the 60′ vertical I have now is quite a bit better than the old 41′ Inverted L (it was actually an Inverted U) on 160M and (barely passable) on 80M. Yesterday I found out that just 7′ of wire difference drastically changes the feed point impedance – that was a real surprise, but I also could tell (as could my KAT-500 and KPA-500) could tell the difference since it made the difference between amplifier faults and working.

I would use the ladder line to go up 63′ and then on one leg – solder a single wire to go up the remaining 7′ – this would go on a 72′ Spiderbeam fiberglass push up mast.

The Low Band Challenge

Trying to build a great DXing antenna on the Low Bands (on a small suburban lot) is quite a challenge. I’ve tried many different things – verticals, phased verticals, shortened top loaded verticals, full wave linear loaded Delta loop on 80, “Mod Bob” using a Palstar BT1500a, switched base loading Inverted L, and more.

And don’t forget the RX antenna – that has taken me a year to experiment for – and with the Wellbrook ALA1530LNP loops phased through the DX Engineering NCC-2 is one of my best antenna accomplishments.

40 meters has always been easy. My DX Engineering DV-40-P is one of the top 3 antennas I’ve ever owned. It’s radial field and siting are perfect (although if you saw it up close you’d not believe it). 160M has been somewhat easy – because I only needed the CW portion of the band.

80 and 75 Meters are a real bugger. I’ve finally come to the conclusion that the best one can do on a small lot is put up one Spiderbeam 60′ fiberglass pole (the 70′ version is $200 more – not worth the money) with wire taped to it and either use relays to switch in different lengths of linear loaded wire or use a Stepper motor to tune for resonance. Another option is to tune for the 80M CW band and then use an in shack tuner for 75M.

My KPA-500 has never liked 80 or 75M. It has had an overshoot problem and also has seemed extra “sensitive” on 75 / 80M. It has been fine on 160M and all other bands. I’ll have to send it in. My K3 and KAT-500 have been fine – it’s just at even more than a couple hundred watts, 75 and 80 get squirrelly. I’m sure it’s a high voltage situation.

One answer is to tune for a small segment on 80M and simply not use the amplifier on 75M. The vertical would be 70′ for 80M and 63′ for 75M. I’ve learned that that makes for a huge difference in impedance at the base.

I think I’ll opt to tune the vertical for 80M and only use the amp for CW, since that’s where the DX pileups are. The net I check into at night, where I never pass traffic, deserves no more attention than 100 watts – hi hi.

So, the low bands really “test your meddle” like no other bands do – both antenna construction wise and then operating wise (at least on the West Coast where EU and AF are considered big catches – a far different cry than for East Coasters).

Its funny how much easier 40 and 30M are compared to 160 and 80M, but I love these challenges, as frustrating as they can be.

History of DXCC Chart – Update

Click on Image to get the full size JPEG, or here for the PDF:


Griffin Powermate as a Tuning Knob for SDRPlay RSP2Pro

The Griffin Powermate is an excellent knob for the SDRPlay RSP2pro. Here is a video on how to set it up:


I’m really having fun with the new RSP2Pro – it plus SDRUno are a great combo – and using the DX Engineering NCC-2 with the two Wellbrook ALA1530LNP loops is awesome – I can’t believe how many AM BCB stations are on the same frequency – and how I can electrically steer them using the NCC-2 knob plus the rotator on each antenna.

DX Engineering DV Phased Arrays and Radials

I have the DX Engineering DV-40-P, and it exceeds my expectations. Unfortunately, the DV-80-P is not going to pan out.

Why? I just found out that it is critical that you have even and equal radials between the two, and that they all be on ground. You cannot have one really good radial field for one and not so good on the other.

I was able to tune each vertical and even get each at 39 ohms. At the Tee in the middle, in the “both” mode, the SWR was ace. But in the shack, and on the air, only the single vertical and both positions worked. The vertical on the deck didn’t do what it was supposed to – show some directionality and also a good SWR.