How do you deal with selectivity problems?

[gcopter1]

I have a Uniden BC125AT and an SDS100. I coonect either to a dipole tuned for the aviation band, on my attic and run an LMR 400 cable to the radio.

When either radio is receiving, I sometimes get bleed over from other aero frequencies.

With the SDS100, I've tried IFX and or filters, to no avail.

With the 125, well, there ain't much you can do.

Was wondering if there were other radios out there, preferably, base model, that weren't so prone to this problem?

 

[wtp]

it means you have too much signal.
attenuation would help.
but if you don't need the antenna, don't use it.
or just put in the hard to hear frequencies into one radio and use the antenna on that one.
i have three older radios and set the antennas up and then put frequencies in to match the antenna.
long antenna gets the low frequencies, the one with the 18 inch antenna gets the 150 stuff and the 6 inch gets the 400.
i can get the space station on a uniden 396T handheld and that is 250 miles away.
so if the airport is nearby you don't need the outside antenna.
my old pro2035 had the attenuation switch on the back and just took a push to change it, now that is real quick.
another thought is to use a TV splitter, then you get 1/2 (50% or -3db) the signal than before.
oh, attenuation is usually -20db and that translates to 1/100 the signal.
i hope it makes sense.
todd

 

[gcopter1]

I live within 3 miles of the airport. With the discone, I cannot get the ATIS. The dipole, in the same spot, pulls it in. That's why I'd like to settle on the dipole but with a different radio. Never had any luck with attenuators, I'll give it a try, though.

 

[prcguy]

What filters have you tried? Something in the radio or external? Aircraft band signals are not that strong and its usually something like a local fire breathing FM broadcast station that is blitzing the front end of your receiver or creating IMD that will make ghost signals of other signals appear in places they don't belong. If you can identify the source of interference you can sometimes fix it with a notch filter or get a band pass filter that only allows the VHF air band to get through and cuts out the FM broadcast band and everything else.

I have a Uniden BC125AT and an SDS100. I coonect either to a dipole tuned for the aviation band, on my attic and run an LMR 400 cable to the radio.

When either radio is receiving, I sometimes get bleed over from other aero frequencies.

With the SDS100, I've tried IFX and or filters, to no avail.

With the 125, well, there ain't much you can do.

Was wondering if there were other radios out there, preferably, base model, that weren't so prone to this problem?

 

[gcopter1]

On the SDS100, the software filters. I do have an AOR, band pass filter, can't recall if I've tried that yet.

 

[prcguy]

You need something external to fix an overload or IMD problem. You can get an idea if it will work by using an attenuator built into the radio, but you don't want to have that in line all the time reducing your sensitivity and range.

On the SDS100, the software filters. I do have an AOR, band pass filter, can't recall if I've tried that yet.

 

[spanky15805]

prcguy

"local fire breathing FM broadcast station that is blitzing the front end of your receiver"

Made me laugh because it's so true. If this forum really understood how much noise they generate and how it affects the air band. Almost like an EF-111A flying around your house, you will hear nothing. Kinduva out of context but I'm pretty sure you seen the movie a couple dozen times.

 

[nanZor]

If your airband needs are simple, one suprisingly inexpensive Uniden has a nice airband front end - the BC355N.

Sure, you have to use the "private bank" for your custom memories, no alpha, and very simple ops. Frequently used in multi-setups monitoring a single channel for streaming, etc. At 60 feet on top of a building in L.A. no noticeable intermod or desense detected with a DPD airband half-wave vertical up there.

Then again, we didn't have any adjacent frequencies programmed like it sounds like you might have.

We hooked it up just to see it jump off the table, and were blown away by the opposite result. Not my daily monitor to be sure, but could suffice if again your needs are simple.

 

[Ubbe]

Try a FM trap filter first. Most of the time it helps a lot when receiving VHF air. Some of them attenuate a lot at 118Mhz but if you don't have anything you would like to receive there, it would still be usuable.

/Ubbe