Microire bandwith

[Andy Durbin]

I measured the bandwith of my Microire receiver. Test method was to
set the receiver squelch just above trip point then to sweep an rf
generator across the set frequency. The points at which squelch
tripped were recorded from the frequency counter built into the rf
generator. Results for the Microire and for an STS handheld were as
follows:


VHF Comm. Measurements 12/16/03

MicroAir:

Pass-band for squelch trip 123.2930 to 123.3070 = 14.0 kHz

STS:

123.2879 to 123.3121 or 24.2 kHz

This appears to confirm the speculation in an earlier thread that the
Microaire receiver has a narrow bandwidth and will be less tolerant of
off frequency transmitters.

I won't know if this explains the audio distortion heard when
receiving some transmitters until I can do a check on the transmit
freq of those units.


Andy

[Andy Durbin]

(Andy Durbin) wrote in message >...
> I measured the bandwith of my Microire receiver. Test method was to
> set the receiver squelch just above trip point then to sweep an rf
> generator across the set frequency. The points at which squelch
> tripped were recorded from the frequency counter built into the rf
> generator. Results for the Microire and for an STS handheld were as
> follows:
>
>
> VHF Comm. Measurements 12/16/03
>
> MicroAir:
>
> Pass-band for squelch trip 123.2930 to 123.3070 = 14.0 kHz
>
> STS:
>
> 123.2879 to 123.3121 or 24.2 kHz
>
> This appears to confirm the speculation in an earlier thread that the
> Microaire receiver has a narrow bandwidth and will be less tolerant of
> off frequency transmitters.
>
> I won't know if this explains the audio distortion heard when
> receiving some transmitters until I can do a check on the transmit
> freq of those units.
>
>
> Andy



I really fat fingered that post. It should read Microair.


Andy

[Steve Pawling]

Thanks for checking this out Andy. The question now is what can be
done about it? It's bad enough having to listen to the unnecessary
chatter on 123.3 and .5 but when half of it is distorted and
unintelligible I just turn off the radio.

Tim Mara - do you have knowledge of a solution to this problem? Any
help from Microair?

Steve
LS3a AM w/Microair 760

(Andy Durbin) wrote in message >...
> I measured the bandwith of my Microire receiver. Test method was to
> set the receiver squelch just above trip point then to sweep an rf
> generator across the set frequency. The points at which squelch
> tripped were recorded from the frequency counter built into the rf
> generator. Results for the Microire and for an STS handheld were as
> follows:
>
>
> VHF Comm. Measurements 12/16/03
>
> MicroAir:
>
> Pass-band for squelch trip 123.2930 to 123.3070 = 14.0 kHz
>
> STS:
>
> 123.2879 to 123.3121 or 24.2 kHz
>
> This appears to confirm the speculation in an earlier thread that the
> Microaire receiver has a narrow bandwidth and will be less tolerant of
> off frequency transmitters.
>
> I won't know if this explains the audio distortion heard when
> receiving some transmitters until I can do a check on the transmit
> freq of those units.
>
>
> Andy

[Andy Durbin]

(Steve Pawling) wrote in message >...
> Thanks for checking this out Andy. The question now is what can be
> done about it? It's bad enough having to listen to the unnecessary
> chatter on 123.3 and .5 but when half of it is distorted and
> unintelligible I just turn off the radio.
>
> Tim Mara - do you have knowledge of a solution to this problem? Any
> help from Microair?
>
> Steve
> LS3a AM w/Microair 760


Steve,

I hope my post didn't suggest that the Microair narrow bandwidth is a
problem. 8.33kHz channel spacing will force all manufacturer's to
reduce intermediate frequency *IF* bandwidth from that used for 25kHz
spacing radios.

When the 8.33kHz channels are populated, users of 25kHz receivers may
start to experience adjacent channel rejection problems. Perhaps
Microair is one step ahead.

I still don't know what causes the distortion, but hope to make more
tests using the glider radio that is always a problem for me.


Andy

[Steve Pawling]

Yes, I agree that narrow bandwidth isn't (and shouldn't be) a problem.
However, a radio that can't perform in the real world IS a problem. I
assume that all of those "loose" radios will be in use for many years
to come so maybe Microair needs to come up with some circuitry that
assures clear reception from all radios currently in service.

What about other radio brands? Do their latest models also have narrow
bandwidth and the distorted reception problem?

Steve

(Andy Durbin) wrote in message >...
>
> Steve,
>
> I hope my post didn't suggest that the Microair narrow bandwidth is a
> problem. 8.33kHz channel spacing will force all manufacturer's to
> reduce intermediate frequency *IF* bandwidth from that used for 25kHz
> spacing radios.
>
> When the 8.33kHz channels are populated, users of 25kHz receivers may
> start to experience adjacent channel rejection problems. Perhaps
> Microair is one step ahead.
>
> I still don't know what causes the distortion, but hope to make more
> tests using the glider radio that is always a problem for me.
>
>
> Andy