[HCARC] Antenna noise

[SARA SANDSTROM]

Ray, 

Don't feel bad.  My guess is 90% of hams are running preamps when they shouldn't be (and complaining about splatter and interference).  More gain is better, right ?  Anyway, the easiest thing to try is just turning the preamp off.  Be sure to note how many signals you can hear in each configuration.  In the old days, pre-digital TV, about the best 10 m test signal was the 8th harmonic of the 3.5795 MHz color burst signal in analog color TV's which showed up about 28.6 MHz.  Unfortunately those days are gone, but if you have an old analog TV around you might try to hear it.  It was also a good six meter test signa l 50. 114 MHz. 

Good luck, 

Kerry, K5KS  


----- Original Message -----

From: "Ray Owen" <rowen at owencomps.com> 
To: "SARA SANDSTROM" <kerryk5ks at hughes.net> 
Cc: hcarc at mailman.qth.net 
Sent: Saturday, July 13, 2013 8:10:12 PM 
Subject: Re: Antenna noise 




I’ll try it without the preamp.  If that’s all it is I’m gonna feel like the village idiot LOL. 
  
Ray Owen 
Owen Computer Solutions 
830.998.0914 
KF5VNC 


  

From: SARA SANDSTROM 
Sent: Saturday, July 13, 2013 8:02 PM 
To: rowen at owencomps.com 
Cc: hcarc at mailman.qth.net 
Subject: Antenna noise 
  



Ray, 
  
The issue is not the high noise from your dipole.  Antennas aren't all equally efficient.  Mobile antennas are notoriously inefficient.  If one antenna is more efficient, the noise it receives will be stronger than the noise the inefficient antenna receives.  Does your receiver/transceiver have a preamp?  If it does, turn it off and see what the noise on the dipole is like.  The important thing is not S-meter reading but signal-to-noiose ratio.  Do the signals have the same SNR on the two antennas?  If so, turning off the preamp when you use the dipole may be all you need to do.  It is possible that the difference in polarization between the mobile antenna and the dipole is causing a stronger signal on the dipole or it may be the dipole is closer to the noise source than the mobile antenna but that isn't where I would start.  Do you hear the same signals on both antenna?  Do you hear more signals on one antenna or the other? 
  
If you have reasonably good antennas and receiver, you shouldn't need an RF preamp on ten meters or actually on any HF band.  The only antennas that really require a preamp are Beverage antennas, short whips (~1 meter tall) or small loop antennas.  45 years ago the best receivers had either very little RF amplification with extensive tunable RF and IF filters or no amplification before the mixer.  With the waves of "rice boxes" arriving on our shores, we seem to have forgotten what we used to know.  The rules still haven't changed, RF gain should be minimized in a truly high performance receiver.  
  
Let me know if you try these tests and how you make out.  I'll be happy to answer any questions. 
  
You will probably get a lot of different answers to your question.  Try everything 
  
Kerry, K5KS