Survivalism & Self Sufficiency Topics > The HAM Radio Board

2200 meters and 630 meters now open to amateurs in the USA

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LodeRunner:

--- Quote from: Alan Georges on March 31, 2017, 06:50:10 PM ---I'm guessing that these bands will be best for blanketing a small area with signal...

The one thing that looks really interesting is ground wave propagation over salt water. 

Interesting ham geek stuff, but I'm not sure how relevant it will ultimately be to what we discuss here at TSP. 

--- End quote ---

Alan,

On 630M there is substantial skywave at night. There can be decent Trans-Polar Skywave, even during daylight.   
Skywave propagation on 630M is essentially global when the D-Layer is not ionized by the sun.  Even with the limited emission power of 5Watts EIRP intercontinental contacts are proving to be pretty easy  to accomplish.

On 2200M Skywave doesn't really exist - the wavelength is so long that the E and F layers create a kind of "duct" (with the earth as the other side of the duct)  that can conduct signals a long way whether day or night.  So down here in the LF spectrum we still have two main propagational modes, but they are Groundwave and Ducting.  This is what makes LF (and VLF, wish we had a band down there!) so interesting...

On 630M you can get between 5% and 10% efficiency with a 'typical' transmit antenna, i.e. using a G5RV as a Marconi-T antenna worked against a substantial ground, or an 80M or 160M Inverted-L antenna - again, worked against a substantial ground.  With such a setup, the key concerns are minimizing losses in the resonating coil, and maximizing the GROUND portion of your setup.  So, at 10% efficiency you would need 35 watts of transmitter output to get 5 Watts of EIRP --- Yes, 35 watts, not 50 watts; because the "I" in EIRP stands for Isotropic, and a real antenna doesn't radiate evenly into a full sphere (Isotropically), it radiates into *roughly* half a sphere, so you have to reduce power by another ~2.8dB. 
35~75 Watts is easy to produce with a simple amplifier, and that plus about 400uH of matching coil is all you need to max out at 5W-EIRP with reasonable (suburban lot sized) antennas.  And you need a good ground - see the description below under 2200M antennas.

2200M is a very different story.  Even 1% efficiency is hard to achieve with antennas that fit in a typical (suburban sized) ham's antenna farm.  What this means is that you're going to need 100 to 250 watts of power out of your LF amplifier to get close to the 1Watt EIRP limit - again, using an existing HF antenna such as a G5RV or Inverted-L
plus a BIG matching coil (1 to 5 miliHenries - figure 1 foot diameter, 2 feet long) and a really good ground - figure 20 radials, each `50' long, plus several ground rods.

As for which modes to use - CW, JT9/WSPR, Olivia, QRSS and DFCW are all common down on LF/MF.
For CW, and Olivia I'd use FLDigi.  For JT (and WSPR) there's WSJT/WSJT-X, and for QRSS and DFCW theres Spectran (simple to use) and Spectrum Lab (very complex) plus Argo (older, runs well on very old computers).

Regional coverage on 630M is excellent, even with modest antennas.  That's where I'd recommend you start your LF/MF journey. 
2200M is for the "advanced builders" in the crowd who want  a technical challenge.

antnn1:
LodeRunner,  I know this is an older post, but had some questions if you're still active on here (tried sending a private message to you but it comes up as error).   So we can use an existing 160M inverted L on the 2200 & 630M bands, with a good ground radial plane & seperate loading coils. 


-If the ground radials for a 160M inverted L consists of about 33 wires at 100 ft long each, would that be good enough for the 2200 & 630M bands?


-You mentioned that you use your 160M inverted L for the 2200 & 630M bands (with coils).  How many ground radial wires do you have, & what are the lengths?


Thanks

Mr. Bill:
LodeRunner is no longer a member here.  But maybe some other knowledgable members can answer you.  (Sorry, that doesn't include me!)

Also, welcome to the forum!

exSun:

--- Quote from: antnn1 on June 20, 2020, 03:57:58 PM ---...
-If the ground radials for a 160M inverted L consists of about 33 wires at 100 ft long each, would that be good enough for the 2200 & 630M bands?
...

--- End quote ---

Define "good enough." Note that the allowed ERPs for these bands are very low. The low power usually results from running a lot of power into a very inefficient antenna system. Unless you are blessed with 500 foot tall towers you won't have an efficient system on 630m. And unless you can hang a curtain from one side of a large valley to the other, with miles of ground counterpoise, you won't have an efficient system for 2200m. So take what you have, do the best modeling you can to get the estimated efficiency, then do what you can to approach the allowed ERP and you will certainly be able to be heard by somebody, somewhere.

-Chris

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