Secure Site Login


Joined: Sat, Apr 4th 1998, 00:00 Roles: N/A Moderates: N/A

Latest Topics

Topic Created Posts Views Last Activity
Forums demoted? Aug 18th 2013, 18:36 10 3,518 on 28/8/13
Why isn't there more action on ARRL forum? Sep 13th 2012, 00:48 11 10,309 on 29/1/13
Forum avatars? Aug 17th 2011, 16:45 5 4,101 on 21/8/11
Operating Furniture Aug 17th 2011, 01:52 10 8,252 on 27/12/12
Radiolocation News Jul 27th 2011, 01:52 3 4,206 on 28/7/11
General Comments Jul 24th 2011, 21:46 22 12,114 on 29/7/11

Latest Posts

Topic Author Posted On
QRN from neighbor's air compressor N0CHS on 13/7/18
Older air compressors (like mine) have normal (induction) AC motors that don't usually make RFI. If your neighbor has one that has a variable speed motor, they can make a lot of RF noise. The easy check would be to take a portable radio (AM, FM, or shortwave) to the compressor and see what you get. Chances are the interference is very broad band. In any case you should be able to check out various parts (the motor, the line cord, etc.) to see which are "hot". Most likely, it is injecting noise into the AC power line, so a filter on that line might help. You might also check to see if the frame is properly grounded to the AC 3rd wire.

Good luck!
Martin AA6E
FT8 WD5IQR on 29/8/17
FT8 is now handled as a mode by LoTW in latest versions of TQSL. See (LoTW login required)
HF use of squelch wheelgunnut on 22/8/17
Bill -

Squelch is more useful with FM than with AM/SSB because FM signal quality falls to pieces very rapidly when it weakens toward the noise level. (Threshold effect) AM/SSB signals, on the other hand (particularly SSB), degrade more smoothly as they get weaker. You can still copy signals that are near the noise level. With effort!

Also, HF propagation is often more variable than VHF+. You might want to copy a signal that varies between S3 and S9 over a few seconds. Squelch might cut out the dips when you could still copy them.

You can reduce the "noise blast" after a transmission stops by adjusting your AGC or RF gain controls carefully.

It comes down to personal preference, but most ops seem to prefer to keep their "ears" open as much as possible on HF/MF.

73 Martin AA6E
FT8 AG5P on 13/8/17
**ADDED** Latest update of TQSL and LoTW support FT8 without any fuss. Disregard following.

Easy workaround:

Select File > Display or Modify Prefences...
Select ADIF Modes tab
Add... ADIF Mode = FT8
Resulting TQSL mode: DATA

Now, when you run TQSL, ADIF file's FT8 QSOs will be mapped into DATA QSOs for LoTW. ARRL awards category DATA is the same as JT65 and other digital modes. It would be nice to record your Q's as FT8 in LoTW, but it's not necessary.

73 GL Martin AA6E
Electric Field Strength Limit Calculation kj4saf on 31/7/17
Which FCC rules are you referring to?

The basic rule has to do with PEP output power level with no reference to field strength or antenna gain.

If you are referring to the RF exposure (safety) rules, the considerations are different, and rather more complicated. I recommend you consult, if you haven't already done so.

Your calculation seems to be on the right track -- You are looking at the field strength in the far field of an isotropic radiator. But we are rarely in the far field (certainly not for common frequencies at 3 meters separation), and our radiators are never isotropic!

Actual electric field strength depends on many things - distance from radiator, antenna radiation pattern and gain (including transmission lines), polarization, as well as power level and environmental details. It's hard to make an accurate calculation from first principles. Mostly, amateurs are well advised (IMO) to use the broad "safe harbor" rules that say that for a certain frequency, separation distance, and power level you are OK without doing a precise measurement. (And the level is different if you're talking about yourself or your family vs the general public.) If you come close to the "danger" level, then you are supposed to do a real measurement to show that you're OK -- or else reduce power.

73 Martin AA6E

Back to Top