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SDS100 Possible Interference

KK4JUG

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#1
We just had some nasty weather pass through the area. I had the SDS100 and a Yaesu VX6 portable out to listen to SkyWarn and public safety reports.

The 100 would occasionally cut out in the middle of a transmission. I got the 436 out and it was working fine. I did not transmit on the portable but could the proximity of it cause the problems with the 100? They were about 6" apart.

The 100 is working fine now.
 

TailGator911

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#4
I researched this when considering antenna placement on the roof of my RV, curious as to the interaction between different receivers. As we know, you have to be careful with TX around any RX antennas, but two RX only antennas/radios in close proximity to each other can sometimes induce crosstalk on the radios. If the antennas are too close together they can induct together and blend as one and sometimes imaging can occur as well as bleed-over, 'dropouts' and multi-path interference. 1/2 wave distancing between antennas is the rule of thumb. So I have been told. If both radios - placed only 6 inches from each other - are receiving on the same band, your scanner might have been experiencing 'dropout'. I just asked my hammy guru on local 2-meters (Obie Wan Cannoli) and this was his explanation. Sounds plausible to me.

JD
kf4anc
 

k5xs

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#5
...If the antennas are too close together they can induct together and blend as one and sometimes imaging can occur as well as bleed-over, 'dropouts' and multi-path interference..."
JD
kf4anc
That sentence makes absolutely no sense to me. I don't know what "induct" together means, and imaging takes a whole lot more power than I suspect either receiver's LOs can generate. And multipath has to do with signals arriving over different paths.

I think it's far more likely the OP has a scanner problem.
 

TailGator911

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#6
As it was explained to me and passing it along, I apologize if this is misinformation. Myself, I did not think 2 scanners 6" apart would affect one another, as I have more than a few stacked together and have no problems with reception. Add to that, I often have 2 or more HTs and HH scanners in close proximity to each other when mobile and no problems whatsoever. I take care not to transmit too close to an RX antenna, of course. Sometimes I think Obi Wan just likes to hear himself talk lol. He was on the Net so I asked him the question. Hey just trying to help~!

JD
kf4anc
 

KK4JUG

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#7
I think it's far more likely the OP has a scanner problem.
OK, I don't want to hear that.

Tailgator, the 100 was receiving 800 mHz, the portable was receiving ham VHF.

One thing I forgot to mention: there's a laptop computer about 1½ feet away.

I'm gonna experiment a little. It may be something as simple as antenna location. The radio works fine in other locations.
 
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#9
Bad weather with heavy rain often attenuate radiosignals enough to make reception problematic. The higher the frequency the more it is affected. The SDS100 receiver are not as good as the one in a 436 so I would regard it normal that a 436 works better than a SDS100 under extreme conditions.

If it happens again you could look at the signal strenght to see if it's weak, or configure the display to show d-error and noise level to more easily see if signal levels go down too much in bad weather. Also remember that wave lenghts at 800MHz are very short so that moving the antenna just a couple of inches could move it to a position of total blackout depending of frequency and direction to the signal source.

/Ubbe
 

KK4JUG

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#10
I believe I figured it out. I put the radio back in the location where the signal was dropping out. When it happened, I immediately moved the radio and the transmission reappeared. I did it several times and decided it was simply antenna location.
 
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