I recently installed a Palomar 160 EF (173' with the 1500W UNUM). All bands 6-80 are 2.0 SWR or less (untuned/matched) except for 160. It's closer to 6:1 according to my tuner (yet 2.5 per LP-100A). At any rate, the tuner brings it to 1.5. All works fine on all bands (except 160) with 100-500W from my Flex PGXL. However, when the output exceeds 150W at 160 M, the SWR exceeds 2.0, and the amp reduces power out and gives the usual warnings. Mode is FT8. I installed it per instructions, the feedpoint end is at about 50-60' and ends at 15' with the last 10' of wire being used as a vertical radiator. I have the supplied Choke 80' from the feed point for counterpoise. Using a 1:1 isolator outside the shack. Run is appx 135' of LMR-400. No separate counterpoise installed, as per instructions, it is not necessary. May add 80-100' to it this weekend to see if that helps. Thoughts?
-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
-
A Winner has been selected for the 2025 Radioddity Cyber Monday giveaway! Click Here to see who won!
SWR jumps when power is increased
- Thread starter W4ABF
- Start date
Antenna analyzer? Buy, beg or borrow one and run a sweep of antenna. Will let you see what's up for every band but especially where it's resonant on 160m. Could be resonant below the band portion you wish to use. May allow you to tune 160m without trashing the other bands. SWR doesn't tell the whole story.
Last edited:
If the mismatch increases with power level increase, two possibilities emerge. Either the amplifier's signal purity suffers as the power increases and it's adding a second frequency not in the band you're tuned for.
Or the core of an inductor is saturating past 150 Watts, reducing its inductance beyond that power level.
Neither one sounds likely, but that's what comes to mind.
73
Or the core of an inductor is saturating past 150 Watts, reducing its inductance beyond that power level.
Neither one sounds likely, but that's what comes to mind.
73
Thanks - I have a MFJ but it's headed for the recycle bin. I have a AURSINC NanoVNA SSA-2N V2.2 as well as a RigExpert AA-35 on my Amazon shopping list, deciding between the two. Suggestions?
Good ideas - both. I only experienced this on 160, so it could be either. Bob Palamor replied quickly to my question and suggested an 80-100-foot counterpoise in addition to the coax. When it warms up a bit, I'll try that. The UNUM is rated for 1500w PEP. It behaves normally at 500w FT8 on 6-80, so I'm thinking I just need to move the UNUM around a bit and add a counterpoise.
For $25 plus shipping, it's yours. It works as advertised, just looking for an upgrade. My address is good on QRZ, is yours? PP to philliphare1@gmail.com
That's why I got a AA-55 Zoom for HF and 6m. Pristine used on QRZ for a good price.
And you're right, the Rig Experts for UHF and up are very pricey. Why I don't have one.