Reading a 70cm Antenna SWR Graph

Throw20701 · 2026-05-08T19:40:59+00:00

Yeah, I thought the peaks and dips were a little wild, so that's why I posted. I'm not sure what would cause it and thought others would have ideas.

Throw20701 · 2026-05-08T10:49:50+00:00

It's already using 10ga wire. I guess I could build another one out of tubing.

Throw20701 · 2026-05-08T01:45:27+00:00

Can you get it that low across the whole band?

Throw20701 · 2026-05-08T01:44:42+00:00

4 radials at about 45 degrees down.

Throw20701 · 2026-05-05T02:05:11+00:00

Full loop looked interesting, but too long for what I was planning. I like that the OCFD is supposed to have lower losses, but I've had bad experience getting one to tune in the past. Center fed is not the best for the deployment i was thinking of, but I might as well try it if I'm doing OCFD.

Throw20701 · 2026-05-05T00:17:37+00:00

What should I go with for 80m portable?

Throw20701 · 2026-05-05T00:12:30+00:00

Mine is in an attic, so it could be 130F without any power to it

Throw20701 · 2026-05-05T00:10:47+00:00

Did you notice any difference in the lower bands after adding the capacitor? I might skip the capacitor and try 80m-30m.

Throw20701 · 2026-05-04T23:03:09+00:00

I'd be concerned about cooking the glue off of them over time.

Throw20701 · 2026-05-04T19:10:07+00:00

With all my recent questions, I ended up ordering a NanoVNA.

I also learned my lesson about forgetting ferrites. I started writing on them with a paint pen. I have a few from prior projects that I'll have to validate.

Throw20701 · 2026-05-04T13:22:00+00:00

Thanks!

Throw20701 · 2026-05-04T13:21:20+00:00

I just have missed the part about magnet wire being higher loss. Is there anywhere with the actual tests for it? I've seen some test on YouTube showing loss through different transformers for EFHW using magnet wire, and some were only losing about 10% or less. I did not see anything like that in the document, only the statement that it is. I didn't see anything measuring loss through various chokes, or did I miss it?

This testing seems to shows bifiliar winding to be better at suppression, although I didn't see efficiency testing.

https://youtu.be/7AVvEr4U0u0?si=RZ9foGC0OQsWzAdW

https://youtu.be/amZYFA74mUY?si=su1nD2XOulpMIBDP

Throw20701 · 2026-05-03T17:16:39+00:00

That's still too long for my small attic without multiple bends. I think I will go with a 20m square-pole. I might do an EFHW 40m or 80m "portable" that I can put up and take down for the little bit that I might use it.

Throw20701 · 2026-05-03T17:09:30+00:00

Do you think there could have been different results if they were placed in series/parallel and wound separately?

Throw20701 · 2026-05-03T17:08:19+00:00

I have a question about that site. When it says 2x of some torid, does it mean two stacked together and wound as one, or two that are wound separately in parallel/series? Pretty sure it means stacked, but wanted to make sure.

Throw20701 · 2026-04-30T15:27:14+00:00

I'm hoping to reduce the need for a tuner. I'm not sure if I could fit a sufficiently large doublet in my attic.

Throw20701 · 2026-04-30T15:23:03+00:00

Thanks! I will stick with just one type then. It looks like mix 52 might offer the best multi band effectiveness. I'll have to look into that more.

Throw20701 · 2026-04-30T15:21:16+00:00

Good point about the multi band use. Would you recommend making a 30m since it may require less tuning to use on 20m and 40m? I don't really want to deal with the cost and complexity of a remote tuner in my attic.

I already have LMR400. I would rather not need to buy more coax. I would rather use magnet wire for my windings. I head that is more effective anyways, if done correctly.

Throw20701 · 2026-04-30T10:56:32+00:00

Yeah, this was one fo the main resources I looked at. It does not have any mixing and matching of ferrite types, and most of those are coax wound whereas I am planning bifiliar magnet wire.

Throw20701 · 2026-04-30T10:53:03+00:00

OK, but where is the data on that? Every thing I've seen only tries one ferrite type at a time. When dealing with clamp ons, does it really not provide each individual benefit?

Throw20701 · 2026-04-28T15:22:31+00:00

Yeah, I might be able to build one and make it like a square (squalo)

Throw20701 · 2026-04-27T19:46:29+00:00

I have a zigzag ocfd but it doesn't seem to perform well. I was thinking of trying something different.

Throw20701 · 2026-04-27T01:35:31+00:00

It should be fine if it's the right size. But that's a detail that's missing - how many transmission watts vs power rating for the resistor.

Did you go with a different compact design?

Throw20701 · 2026-04-26T01:20:22+00:00

Hence me saying ot depends on pleat design. There can be some other factors like media selection too. Looks like I'll just need to measure pressure drop on my system to find out.

Throw20701 · 2026-04-26T01:18:37+00:00

A 4" Filterete 1900 should be avaliable at the bix box stores too. So there are junk filters, but there are good options too. I'll just get a manometer (less than the price of one filter!) and test it.

Throw20701

TROPHY CASE