Diving into Ham Radio... uh oh!

Grumpycat · Nov 1, 2020

dragoneggs said:
I will probably do some more playing around but here are my measurements if anyone cares. Shown are EFHW-8010-2W Antenna tune measurements: Band / (AS IS antenna length 130ft) SWR, and SWR after antenna shortened 2ft. Sorry I don't know if it is possible to embed a file so here is the raw plain readings I took. The 'red' numbers are well above 3. You can see I sort wiped out my 10m bands trying to tune for 80m.

Tuning the antenna before the license? Naughty, naughty! de N4HHE

OK with something ultra low power such as a nanoVNA but not with a transceiver and tuner.

Fixation on SWR is soooo CB. You would like the antenna to be resonant in transmitting frequencies but the big concern is reflected power. Not the ratio of forward to reflected.

Industrial Toys · Nov 1, 2020

But isn't any power being produced that isn't going out the antenna, coming back? Where else is it going?

Grumpycat · Nov 1, 2020

Industrial Toys said:
But isn't any power being produced that isn't going out the antenna, coming back? Where else is it going?

It bounces back and forth. Losses attributable to SWR are minimal. Can heat the finals in your transmitter so it is not good. But "SWR" is something that seems to have one if the most successful marketing departments known to man the way newbies and others obsess.

A 3:1 VSWR results in 1.2 dB power loss. Path loss through the ether may be 100 dB. 140 dB for GPS.

Industrial Toys · Nov 1, 2020

Isn't the situation more dire at higher frequncies?

Grumpycat · Nov 1, 2020

Industrial Toys said:
Isn't the situation more dire at higher frequncies?

Nope. Exactly the same.

Higher frequencies have a lower noise floor which helps hear signals which would fall below the noise on other frequencies. Is little use to build radio front ends with low internal noise for HF (<30 MHz) than for 2m (144-148 MHz) and above.

There is loss with impedance mismatch but tuners do not cure that, they only keep it away from the transmitter.

Industrial Toys · Nov 2, 2020

I remember running this ANDREWS 1-5/8" stuff up my tower for my UHF Repeater. I always assumed everything got worse as operating frequency went up. HF seemed so easy except for the real estate required for the antenna.

dragoneggs · Nov 2, 2020

Industrial Toys said:
View attachment 675268

I remember running this ANDREWS 1-5/8" stuff up my tower for my UHF Repeater. I always assumed everything got worse as operating frequency went up. HF seemed so easy except for the real estate required for the antenna.

In my case I have the real estate... the 'polluted' view is the problem for both my wife and/or neighbors depending on my placement.

Industrial Toys · Nov 2, 2020

Ham friend of mine was telling me how he excorised (sp?) his house for RFI. Last issue was some LED pot light PSUs making a ton of noise.

dragoneggs · Nov 2, 2020

Industrial Toys said:
Ham friend of mine was telling me how he excorised (sp?) his house for RFI. Last issue was some LED pot light PSUs making a ton of noise.

I have a battery to hook up my rig so I plan to shut all house power off and start diagnosing the sources. Maybe this afternoon when my wife leaves for town.

I have a desk lamp in my home office/shack that is now coming on for 'no reason'. Maybe that has to go? Should be interesting to isolate and reduce RFI sources. I'm guessing this won't be a quick task.