Need Help With Signal Strength Variation

[WRFE959]

I am still working on a reliable base station. Several local repeaters available to the east, west, which I can reliably hit, and further off to the north which I have not been able to hit with my base station. 
 

Elevation at my house is not great. I have done the best I can right now with antenna height.  Tram-1486. 

25 foot M&P hyper flex 13 coax  

50 watt mobile radio with good power supply. 
 

My receive signal quality varies significantly throughout the day. I always have noise in the back ground but some times the noise is low and signal strength is strong. Other times noise is very high and signal strength is weak. When signal strength is weak, the best local repeater may not even hold the squelch open. 

I know the noise would drop if I could get more height.  In my mobile setup just a mile or so from the house and probably 50 feet of elevation gain, most of that noise goes away.   But I can’t move the house, and I am at max height for now.  Just trying to understand the variation throughout the day.  I would be very happy with the good signal times.  But the bad times are very bad. 

I have noticed stronger signal in the morning and evening in general but that is not always true. Some evenings still a weak or varied signal strength with high noise floor. 
 

I can also observe fluctuation in direction.  When the repeaters to the east are strong the west repeaters are weaker. And vice versa.  
 

Can someone give me an explanation about the cause of this type of variation. Is it weather conditions? Does the sun effect the signal quality?

 

Will a higher gain yagi antenna make a difference in this type scenario?  I have read some comments about more gain improving signal receive but would like to hear some confirmation of that before I go through the trouble of switching to a yagi with a rotator.  I would prefer to stay with the Omni antenna.  But I need to work on signal strength.  
 

Any words of advice from someone with more base station experience?

 

 

[axorlov]

UHF signal is not affected by sun. UHF signals are sometimes (rarely) susceptible to reflections in atmosphere between the layer of  colder and hotter air. If you noticed correlation of you signal changes with fog or low cloud cover, that may hint to this type of propagation. Another, and more probable reason of change over the course of the day is that you have a business transmitter/repeater in the UHF band nearby. If you notice worse reception in the work hours, that may be it. This transmitter may make your radio go deaf. There is also a remote possibility that something in your house creating an interference. Remote because we are talking about UHF, but still a possibility.

If you're inclined, do some research. Get RTL-SDR dongle for the PC and see what's going on in the spectrum around you, at the times when reception is good and when it's bad. Good dongles (Nooelec and rtl-sdr.com) are below $40 these days. And they used to be below $20, I've got mine in ole goode times before covid.

Yagi will help for sure, but rotator is a pain, and maybe there is a easier solution.

[WRFE959]

Thanks Alex.

That's helpful.  I'll follow up on the idea of another RF source somewhere.  RTL-SDR is a good idea.  I have been interested, but not taken that step yet.  I did not think of it as a troubleshooting tool for this issue.  

I did try ruling out interference from my end, and did not find anything.  But with your comment, I am going to put some more effort into that as well.

"Yagi will help for sure, but rotator is a pain, and maybe there is a easier solution." - Do you have suggestions for a better/easier solution?  I have a 12-element yagi, and used it at lower elevation without a rotator.  But decided to push for height with the omni first.  I would like to explore any other options before going to the yagi-rotator setup.  I understand that can present new challenges, more equipment to fail, finding a good rotator, etc.

 

-Scott WRFE959

[axorlov]

48 minutes ago, WRFE959 said:

Do you have suggestions for a better/easier solution?

Hypothetically speaking, if you find a strong transmitter nearby, and you can lower your antenna to shield it from said transmitter with your roof/house, it may improve reception of signals you are interesting in. That's strictly hypothetically speaking. Maybe there is no strong signal, and maybe it's on the same side of the house. That's just an example. Another hypothetical example is to use 3-element yagi, instead of 12-element, and mounted it with low/null toward the strong interference. It may give you enough of an angle to receive all interesting repeaters, but will block the interference, while being stationary. Just another example.

[KAF6045]

One thing not mentioned is the possibility for the noise to be some form of intermodulation. The other RF sources may not be on GMRS frequencies, but are such that they are mixing together to create noise at 462MHz.

[WRFE959]

Thanks Dennis and Alex.  

Sounds like I need to do some RF interference searching.  The SDR is a good idea, and I will start there.

The shielding idea is interesting.  I was lower on the roof line until last week.  So I did have a shielding effect going on.  The lower elevation was a problem, but I did not have this variability like I do now.  That may be an indication of the source of the interference.  Some scouting on google maps and some drives sound like they are in order also.

The lower gain/fixed direction yagi would force me to sacrifice some repeaters.  But it is another idea to get me thinking. 

 

Thanks again guys.