Best radio for Air band?

[michaelscoofield]

My Mil air BPF for 230-380MHz

is in construction now...

 

[G7RUX]

So simply to ask, what filter bandwidth is used on AM in case of IC-208 please?
If it is too narrow, then lack of 8.33k could be an issue for scanning the band.
If it is a bit wider then it would work with let say 10k steps, isn't it?

-m

I believe the AM path uses the FM narrow and wide filters, so 6k/12k (at -6 dB). I am not clear whether one can select wide/narrow when in AM mode on this radio.

Edit: Having read more of the manual and specs it seems clear that AM and AM-narrow are both available, so 12k for standard AM and 6k for narrow AM (these are at -6 dB on the filter...the -60 dB filter width for each is 30 kHz and 20 kHz respectively.

 

[michaelscoofield]

I believe the AM path uses the FM narrow and wide filters, so 6k/12k (at -6 dB). I am not clear whether one can select wide/narrow when in AM mode on this radio.

Edit: Having read more of the manual and specs it seems clear that AM and AM-narrow are both available, so 12k for standard AM and 6k for narrow AM (these are at -6 dB on the filter...the -60 dB filter width for each is 30 kHz and 20 kHz respectively.

Ahh, many thanks. I should read manual own self first for next time...
So, it seems that it should not be big issue with lack of 8.33k for scanning.

 

[G7RUX]

Ahh, many thanks. I should read manual own self first for next time...
So, it seems that it should not be big issue with lack of 8.33k for scanning.

Indeed, although it depends whereabouts you are.

 

[michaelscoofield]

Could you recommend where I should (at best) insert the VHF FM band stop filter, please?

Current config is: Antenna Diamond D777 at 11m on the roof > Airband elliptic BPF at its feed point > Switchable pre-amp then after at the same place > LMR400 coax 15m long down to shack > FT-350E (to be added IC-E208/IC-208H thru splitter)...

Thanks for hints

 

[Ubbe]

It will depend of the quality of the pre-amp and the signal level of interfering signals. A good pre-amp can handle most situation and can be installed directly to the antenna to compensate for any losses in filters.

If you have very strong FM broadcast signals then the pre-amp might need protection by the band stop filter. If it's easy to reach the antenna then the best would be to do a test. If a constant transmission like ATIS can be used then that would be preferred to check when that signal have the best quality when filters and pre-amps are installed at different positions.

/Ubbe

 

[michaelscoofield]

Many thanks!

I am already filtering the Airband 118-138MHz elliptic BPF at the antenna feed point in front of pre-amp. This pre-amp can be bypassed if not needed by remote control. So, I am thinking if it is better to put in front of pre-amp (between BPF and pre-amp) or put it down ito shack directly in front of radio. (to avoid any breakthrough due to imperfection of the feeder shielding...

As you said, the best will be to make some tests on the air using 90km away ATIS... (but just in theory ...?)

-m

 

[G7RUX]

Many thanks!

I am already filtering the Airband 118-138MHz elliptic BPF at the antenna feed point in front of pre-amp. This pre-amp can be bypassed if not needed by remote control. So, I am thinking if it is better to put in front of pre-amp (between BPF and pre-amp) or put it down ito shack directly in front of radio. (to avoid any breakthrough due to imperfection of the feeder shielding...

As you said, the best will be to make some tests on the air using 90km away ATIS... (but just in theory ...?)

-m

Personally, I would put one in front of the BPF, possibly switch-bypassable with the preamp, and another at the input to the receiver. This way you prevent the amp being clobbered by large OOB signals and the one at the receiver ensures there isn't an issue with cable leakage (although that's unlikely.)

 

[Ubbe]

This pre-amp can be bypassed if not needed by remote control.

If that are some kind of generic relay or diode switch then maybe you can have the filter, any filter, in front of the pre-amp and bypass the filter and compare reception quality to check if the pre-amp can handle your local RF situation without filters. It's usually a scanner that have bad specifications. Do you have the name of that pre-amp?

/Ubbe

 

[michaelscoofield]

If that are some kind of generic relay or diode switch then maybe you can have the filter, any filter, in front of the pre-amp and bypass the filter and compare reception quality to check if the pre-amp can handle your local RF situation without filters. It's usually a scanner that have bad specifications. Do you have the name of that pre-amp?

/Ubbe

I would like to test two LNAs.
I have prepared these
Procom PRO-LNAHP-4-3-2
and lowcost TQP3M9037…

 

[G7RUX]

The Procom unit is very good and you won’t have an issue with that.

 

[w8prr]

So, it looks like BCT15X is out.
I found some reviews (incl. my local club friend’s experiences) which says this radio has pretty bad selectivity and low sensitivity…
So my search continues.
-m

Have to disagree.
I run 4 BCT15X's all on air band and find them to be great.
Using a collinear for 150Mhz with 1/2 inch hard line and split with a Channel Master tv splitter and works fine.
There are more expensive splitters that are likely better but works great for me

 

[INDY72]

I run an Uniden BCD396XT with an Nagoya 771, it's actually pretty amazing on rail and both VHF, and UHF air.

 

[Ubbe]

Procom PRO-LNAHP-4-3-2
and lowcost TQP3M9037…

I believe the Procom to be the one used at VHF sites in the 80's. At Procoms webpage it says:
Gain 18dB
P1 +17dB
OP3 +31dB
Noise 1,5dB

Compared to a modern low cost PGA103+ (semiconductor costs $5)
Gain 22dB
P1 +22dB
OP3 +45dB
Noise 0,6dB

As the gain are 4dB higher the P1 and OP3 are also 4dB too high compared to a 18dB gain but the PGA103+ still has half the internal noise and considerable better OP3.

The TQP3M9037 only covers 700MHz to 6GHz so are unsuitable.

/Ubbe

 

[jaymatt1978]

So what did you get????

 

[michaelscoofield]

I believe the Procom to be the one used at VHF sites in the 80's. At Procoms webpage it says:
Gain 18dB
P1 +17dB
OP3 +31dB
Noise 1,5dB

Compared to a modern low cost PGA103+ (semiconductor costs $5)
Gain 22dB
P1 +22dB
OP3 +45dB
Noise 0,6dB

As the gain are 4dB higher the P1 and OP3 are also 4dB too high compared to a 18dB gain but the PGA103+ still has half the internal noise and considerable better OP3.

The TQP3M9037 only covers 700MHz to 6GHz so are unsuitable.

/Ubbe

Thanks for wake up me mate. I have also one assembled board with PGA103+ unused. So, it looks like it's time now to put it on board...

 

[michaelscoofield]

So what did you get????

Unfortunately, neither of the two options for buying the IC-E208/IC-208H came to fruition. One seller stopped communicating when he found out I was from Europe, and the other sold it to someone else (or so he said) ...
So, I'm looking for another one and still using an old FTM-350 as main unit.
-m