[TowerTalk] 160M Antenna puzzlement

Pete Smith N4ZR pete.n4zr at gmail.com
Sun Dec 19 16:14:18 EST 2021


Thanks, everyone, for a lot of thought-provoking advice.  A couple of 
specific comments.

At the base of the antenna I have 2 #31 cores each wound with 12 turns 
of RG-400, in series.  I think that may be about what Jim means by lots 
more turns - I may even have gotten the spec from him.

It seems to me that moving the needed extra length to the far end of the 
horizontal section may be about the best solution available.  To support 
the vertical section, I shot a line over a tall maple with a tennis ball 
launcher and mounted a 2" diameter block with a Delrin pulley wheel to 
the end of the line, with the antenna conductor (#14 stranded, 
insulated)   I appreciate the concern that over time, this may result in 
the antenna conductor breaking due to movement of the trees on each end, 
but this seemed like the easiest way to get the antenna up.  I know that 
I could, probably should have put a fixed insulator at the right place 
in the antenna conductor, and run a rope from that over the pulley, but 
since I don't really knowe how tall the tree is this seemed like the 
simplest approach.

What I'm going to do is haul the pulley up as far as I can, measure how 
much more length I still need, and then drop the end of the horizontal 
section and dangle the appropriate length from the end insulator.

Now on to the RX antenna!

73, Pete N4ZR
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On 12/19/2021 2:50 PM, Jim Brown wrote:
> On 12/19/2021 10:55 AM, Jeff Blaine wrote:
>> For 160 something around 8+ turns & type-31 are the "right" rule of 
>> thumb answers.
>
> Based on my research, a lot more turns. http://k9yc.com/2018Cookbook.pdf
>
> Pete has received lots of good advice in this thread. I'll add this. 
> Base loading is a bad thing, because it places inductance at the point 
> in the antenna that carries the most current, and should be doing the 
> radiating. Better to remember that SWR is NOT a measure of antenna 
> performance, that as Jeff has noted, feedline loss is pretty low on 
> 160M, and that what matters for moderate values of SWR most is whether 
> you amp can put power into it with the help of a tuner. And if 
> practical, I'd replace that length of RG8X with something the size of 
> RG8. OTOH, doubling the number of radials, realizing that length of 
> on-ground radials is not critical, would probably help TX signal more 
> than replacing that coax, and would change the feedpoint Z a bit.
>
> While adding horizontal length is technically a great idea, sometimes 
> that isn't practical. I like Jeff's suggestion of an L-network at the 
> feedpoint, but the design requires either a lot of cut and try, or a 
> sweep of the feedpoint Z with a good vector analyzer whose data can be 
> ported to design software like SimSmith. I'll bet that Pete has 
> neighbors who can do that. And if Pete can send me a suitable sweep, 
> I'd be happy to do a design.
>
> 73, Jim K9YC
>
>
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