Stays the sameI would suspect that it is generating some harmonics. The harmonics are on a frequency that the antenna is not tuned to, and that part of the signal gets reflected at the antenna feed point. A low pass or band pass filter would fix this. If the amp section is being overdriven, that would cause it. Try reducing power to see if it helps.
Something like this would probably do the trick:Stays the same
Ordered oneSomething like this would probably do the trick:
Dee 2000 swr/power meter also I have a analyzer mini 60 they both show 1.0 swrYour radio may be suffering from an issue I have seen on 2 diferent rci69vhp. Mismatched mosfets in the driver or final section can cause oscillation which could explain the higher swr.
What are you using to measure the swr?
When an amplifier or radio goes into oscilation it will output many other frequencies besides the 27mhz that your antenna is tuned for. Your antenna cannot radiate the rf that is outside of its resonance so all of that junk rf comes back as reflect/swr.Dee 2000 swr/power meter also I have a analyzer mini 60 they both show 1.0 swr
I'm going to check a few things here like my jumpers and.coax seems.Just a cobra 29 I have a 1.0 now if I put a 600 inline it also jumps up 2.5-3 so I want to check all coax I never had this problem before going to order new.driver and final also this is new to meWhen an amplifier or radio goes into oscilation it will output many other frequencies besides the 27mhz that your antenna is tuned for. Your antenna cannot radiate the rf that is outside of its resonance so all of that junk rf comes back as reflect/swr.
Because of the way the biasing works on the driver pair and final pair both mosfets in each section need to be matched for capacitance and vt or they will go into oscilation. I recomend replacing the driver and final pair with a set of Infineon Irz24n mosfets from digikey as I have received fakes when buying from ebay.
I have not seen this issue in a 69ffb4 but I have seen it in two 69vhp.
I'll check that I also have a new pres Richard I forgot about I'm going to put that on and check it to see what I getSometimes condensation in between sections of an aluminum antenna can cause swr spikes, I had this issue with my sigma venom until I used a stainless self taping screw to tie all of the sections together and the issue has not came back.
Also check the low pass filter coils in the cobra 29, If they are spread that is letting 54mhz through and when you amplify that you will get reflect. I had this Issue in a 2517 that a previous tech had spread the coils in. When I would run it into a 4pill it would make my swr rise to 3 to 1. After collapsing the coils no more high swr with the amp on.