Son of Mod Bob!

Son of Mod Bob! Page 14-7 from the ARRL ON4UN Lowband DX-ing book Chapter 14 in the ON4UN Lowband DX-ing book is a gem. John shows how to take a 40M half square and feed it just like the grounded loop – and where it then is a close array on 80M with gain. The dimensions in the book call for 72′ wide and…

The Grounded Loop Antenna (Thanks Jan, OM2XW!)

The feed is a simple L-C circuit, left, and the antenna can be switched between being an Inverted U or Grounded Loop, right Jan, OM2XW, wrote and reminded me of an antenna that is in the ON4UN Lowband Book, and one I have never tried. AA7OK has a VERY nice write up with great references at his web site – http://litlisten.com/aok/ As I understand it –…

Inverted L vs. Inverted U vs. Mod Bob

Inverted U on 160, 80 and 30 and half square on 40M Just for laughs, lets compare three antennas that I could have – against what I have now – the “Mod Bob”. An Inverted L would be MUCH better than the Mod Bob. Its something I need to consider – because I could use the u.RAT to tune it. On 80M, the Mod…

Pacificon 2017

I will be presenting during the Pacificon 2017 Antenna Forum on Friday, October 20, from 3:30 – 4:30, and my topic is “Low Band DXing Antennas”. I will start with a survey of all of the low band antennas that you should consider for DX-ing on the bands 160 – 30M, and I will include transmit as well as special receive antennas. The presentation…

The Best Two Antennas I Have Ever Had

For all low bands, 160-30M, my own designed “Modified Bobtail” is a very clear winner. I’ve blogged extensively about this antenna, and the best antenna tuner for this antenna – and my favorite antenna tuner of all time is the Palstar BT1500A. Every feature, knob and button is useful and perfect for the Mod Bob. The best yagi antenna I have ever had was…

Final Notes on the U.RAT

I installed the URAT out back at the base of the “Mod Bob” antenna. I experimented for a few hours and I was able to get a decent SWR on 160, 80, 40 and 30 by doing this: 160M – bypass the capacitors and use a shunt coil at the antenna feed 80M – use the capacitors with that same shunt coil 40M – same…

U.RAT Version 2.0 and Experiments

The u.RAT that I will set up tomorrow will replace the Palstar BT1500A, but only as a test – to see if two Palstar C600 variable capacitors plus one inductor will work on 160M. I expect it will work on 160 and 30M, but not sure about 80M. I split the control box and the drivers so that the Raspberry Pi Zero is in…

The S and Z Match for the URAT

I was going to disassemble the u.RAT and re-use the components, but I have just come into a second variable capacitor – which is the Palstar C600, a true work of art. I am trying to get rid of having a roller inductor in the circuit, but would much rather have a switched inductor. Yesterday I posted this circuit: And the Palstar BT1500A has…

Collins 32-V3 Antenna Tuner Circuit

I stumbled on a suggestion for a balanced tuner circuit that is suggested in an old Collins 32-V3 transmitter manual. The top circuit is one that I am most interested in. I’d love to try it and compare it to the Palstar BT1500A – which works perfectly, but it would be super if I could use the URAT with two variable capacitors and a…

Balanced Vs. Unbalanced Antenna Matching

I’m going to add the URAT to a 70′ tall wire vertical with 96 buried radials, and this is a classic 80M quarter wavelength vertical. Its an unbalanced feed with an unbalanced antenna. It will require an L matching circuit: I like VE7BPO’s diagram, and I am guessing that I will need to wire the variable capacitor and roller inductor using circuit B, but…