What about adding another 88-108 filter after the ZX60-P103LN preamp? Is the first filter working properly?
How much total attenuation do you have after the preamp to the receiver?With this preamp in circuit I have a very high elevated noise floor with FM broadcast showing up all through the 225-400MHz band and other places it doesn't belong.
How much total attenuation do you have after the preamp to the receiver?
It could be that one component are faulty and self oscillate and works as a mixer. Try the preamp directly to the discones coax and then a passive 10-12dB attenuation. And then add a 88-108MHz filter after and then also try the filter before the preamp. You have tried several receivers and they all display the EXACT same intermod/overload problem at specific frequencies so that it is absolutly sure that it is the preamp to blame and not one receiver or spectrum analyzer that can't handle the signal?
Put a 20dB attenuator after the preamp in the current configuration and check that intermod is still there and doesn't change in character so that it is proven that a better preamp or filtering are needed.
You have some incredible high signal levels from the antenna. If the amplifier outputs 20dBm where it starts to go out of linearity and compress 1dB, that equals 2 volts rms RF level that feeds the rest of the system and you will then have an astonishing 0dBm at the preamps input from the antenna.
I have one FM broadcast filter with smd components that if I insert that it creates intermod products that where not evident without any filter. So it can be passive components in a system that creates problems, so try and run "naked" and then add one component at the time. Maybe you have a strong transmitter at the band edges 88MHz or 108MHz and need to attenuate at least 20dB at those frequencies and not just 6dB, that seems to be very little attenuating for a proper FM broadcast filter. In US you don't seem to have anything wortwhile to monitor at 70-88MHz so at least try and attenuate as much as possible at the lower FM broadcast range. Spectrum analysers are terrible receivers, even the $50.000 ones, but you seem to have tested correctly with the 8600 owns attenuator settings, if that sits before any active components in the receiver.
I see, too much of a good thing can be bad. I am curious about your results with/without that preamp, on some steady signal ATIS stations in the low 100's for civilian and 200's for military. Not having the receiver you do, I must heavily filter before adjusting a variable preamp or not amplify at all. FM & MW filters are needed at my location for the inexpensive receivers.
I would not mind the R8600, but I would prefer a 9700 if it had a RX range of 30 - 1.3 GHz. The specs say the RX is limited to the TX range and I am hoping that is not the case. I shot off an email to a buddy who advised he picked one up a week ago to see what the reality is. The 9700 manual does not advise of a wide RX outside of the amateur bands.
Thank you for the feedback. My buddy just confirmed about the 9700 as well. I would be pleased if it covered commercial freqs and if the 7300 had two antenna ports. I would own one of each if they offered what I want. If the 9700 offered 118 MHz RX and up I would be content.
It must be my location. I get a bit of 42.060 out of Springfield, MO but that's about it. There just isn't much down there to listen to and no skip. Mine is hanging in a tree with the top at 30ft.
Do you think RG6 as feedline could be part of the issue?
I don't think RG6 would degrade things too much but try running it on your roof with 50 ohm coax like I'm doing. Maybe its that top element you made? VHF lo skip has been in and out, you should be picking up something. No 6m repeaters in your hood? The COM201B also picks up CB and 10m pretty good around here.