Non-Resonant EF Antenna Wire Lengths

[ultravista]

I have a Palomar Engineers 9:1 HF Unun for non-resonant wire lengths and trying to figure out what length of wire to start with for 160-10m. There are many different recommended lengths from several different manufacturers/expert and the lengths are different for each one. I do not have an analyzer at this point so measuring SWR is not an option. I can run up to 150ft easily.

For those of you with a non-resonant end-fed, what length of wire and counterpoise(s) do you find optimal for 160-10m?

Palomar Engineers 9:1 Unun
* Bands Covered 160-80-40-30-20-17-15-12-10 wire recommendations in feet = 135, 141, 173, 203

Balundesigns 9:1 Unun
* Coverage of 160m through 10m (wire recommendations in feet = 53, 59, 7,2 88.5, 98.5, 124.5, 146, 162, 175

VE3EED the "Best" Random Wire Antenna Lengths
* 29, 35.5, 41, 58, 71, 84, 107, 119, 148, 203, 347, 407, 423

[RobRich]

The basic premise is wanting the wire to at least a quarter-wave lonb at the lowest operating frequency and not wanting a halfwave multiple of any band you intend to use. Just remember directivity off the ends increases as the antenna lengthens and frequency rises.

Receiving or transmitting? If transmitting you are likely going to need a tuner unless the 9:1 and/or feedline has considerable loss - not a good thing for antenna system efficiency - to swamp impedance mismatches to effectively load multiple bands.

Palomar's suggestions of 135' or 141' look okay for operating on 80m through 10m with a decent tuner. See here:

https://udel.edu/~mm/ham/randomWire/

As noted at the linked page, a 17' counterpoise is a rather common starting point. You might find different length and/or more counterpoise wires to benefit your situation, but it can be a huge YMMV, so simply start with getting on the air before delving too far into optimization IMO.

Beyond just the counterpoise, there is also a decent chance for common-mode on the feedline with such an antenna. An 1:1 choke placed on the feedline between the antenna and the house could be beneficial. Again, actual placement is another optimization aspect, so start with getting the antenna working before worrying about tweaking it.

Conversely, it is almost a "whatever" situation if just receiving. The recommended 135' or 141' lengths should suffice for mediumwave through low VHF reception. Again, just expect some directivity off the ends of the antenna as frequency increases.

[~SIGINT~]

I have Palomar Engineers 9LFs end-feds and follow their recommended wire lengths as outlined in the instructions. You have a Palomar Engineers UNUN, use their recommendations. They have tested it for their product. Why re-invent the wheel?

https://palomar-engineers.com/ferrite-products/ferrite-cores/Bullet-50-450-9-1-HF-Unun-200-KHz-30-MHz-500-Watts-End-Fed-Antennas-VLF-SWL-p81264409

Don't forget, the braid from the coax on an end-fed is the counterpoise, although, you can add your own. This is why you need to add a choke at the "Minimum Coax Length (feet)" point. This is not apparent unless you read the application notes.

https://palomar-engineers.com/wp-content/uploads/Bullet-End-Fed-Antenna-Typical-Configuration-Notes-11182020.pdf

This page is a little easier to understand when it comes to lengths to avoid.

https://www.hamuniverse.com/randomwireantennalengths.html

[ultravista]

I would like to work 80-10m, and possibly 160m if I can - transmit & receive.

[~SIGINT~]

I would then stick with the recommended wire lengths from Palomar Engineers for your UNUN.

An antenna length of 135, 141, 173 or 203 ft and a minimum coax length of 130 ft. As the feed line shield is acting as part of the antenna counterpoise, you will need to place an appropriate choke along the feed line at the recommended 130 ft point. The position of the choke along the feed line will "electrically" stop the shield from forming part of the antenna and will also limit common mode noise (CMN) generated between the radio to the choke from travelling forward towards the antenna feed point. Omitting the choke will result in CMN travelling all the way from the radio to the antenna feed point and being radiated out. In turn this is picked up by the driven element and essentially you are injecting static / noise into the antenna. The antenna also has the potential of also transmit this CMN to other nearby antennae thus interfering with reception.

Here is my 9LF with 44 ft of wire, a 16 ft external counterpoise and +/- 70 ft of coax choked at 50 ft. Pretty much as speced by Palomar Engineers data. Don't forget that the internal tuner in most modern transceivers will not tune when the SWR approaches or exceeds 3:1.



This is the same antenna but only 8 ft off the ground. Not so good for TX purposes in the low bands.

[joczo]

I have my endfed "longwire" for years now.
It has a 9:1 UNUN,a tuner next to the radio,and it works 80 through 10 meters.
The wire itself is 35meters long

[Pigmeat]

I've got an old MFJ Random Wire tuner I used for transmitting when I was doing things I wasn't supposed to. 72 ft. is about right for the wire and the coax where I was playing around at. The transmitter ran nice and cool. Seeing that I was using a cheap truckstop SWR meter with it, I was always surprised.