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630 meters




 
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Author Topic: 630 meters  (Read 2818 times)
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ka1tdq
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« on: September 30, 2017, 02:31:15 AM »

The new 630 meter band (472 to 479 KHz) has a maximum ERP of 5 watts.  CW and WSPR modes are there and the modes lend themselves to low power.  Phone operations are allowed there as well, but would it be in poor taste to put an AM carrier in the middle since the band is only 7 KHz wide?  At 5 watts peak, that would work out to about 1 watt carrier if you modulate at a decent level.  

You wouldn't be able to talk to anyone, at all... ever... at that power level.  You could however broadcast an AM beacon similar to a CW beacon.  Just get a voice contest keyer and put it on repeat.  

I was thinking about some quick ballpark figures on a single FET class E rig at those frequencies and the size of the tank components are enormous!  You could scale things down since the power is so minuscule.  Probably a 50 turn miniductor would suffice for the tank coil.  After that, just keep adding 1000pf doorknobs everywhere until things work out.

But actually, the limit is 5 watts ERP.  So, you could technically run a 1kw carrier rig into an 8' whip. That's actually funny... run a 95% efficient transmitter into a 5% efficient antenna. 

Jon
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W1ITT
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« Reply #1 on: September 30, 2017, 12:26:11 PM »

The 630 meter band is really too narrow for SSB, to say nothing of AM, if many people are to enjoy our new allocation. Another consideration is that antenna system bandwidth is likely to be narrow enough, with some configurations, to act as a narrowbanding filter.  This is something that has to be taken into consideration for regular AM broadcast arrays as well.
CW and some of the various digital modes are in order.  Wideband modes on 630m will ensure hate and discontent.
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KD6VXI
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« Reply #2 on: September 30, 2017, 08:40:11 PM »

I was a lowfer op in the late 80s.

The way it has been argued / interpreted is you use a NEC style simulation program to get antenna and feedline efficiency estimates.

Then build an amplifier to.get the legal ERP.

A friend who has an experimental license for the low bands has a few kilowatt amp.  To get 5 watts ERP.

--Shane
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ka1tdq
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« Reply #3 on: September 30, 2017, 10:00:42 PM »

A full length dipole would be almost 1000 feet long.  Efficiency would suffer too because you'd need to get it extremely high in the air. 

I'm sure one of the commercial antenna manufacturers will come out with a good antenna. 

Jon
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« Reply #4 on: September 30, 2017, 10:41:24 PM »

As Shane said, at those frequencies it takes considerable power to effect any field strength.

Field strength is measured with a calibrated receiver, and from that a required ERP (effective radiated power) combined with plotted antenna efficiency, is derived.

Antenna efficiency vs. input power calculations yields TPO (transmitter power output).

Having a 1kW TX to get 5W ERP is very close to real world amateur antennas.

In short, hams are not limited to 5W transmitters here.

73DG
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« Reply #5 on: October 01, 2017, 12:39:42 PM »

When I did lowfer ops, I got a very wideband car stereo amp.....  Black Magic, I believe the brand or name was.

Mono bridged, it did a few hundred watts.  Into 8 ohms.

It had no transformer on the output, it was BTL design (balanced transformer less design).

Worked great for the school year I operated it.

Then I got a car, and the amp went to its intended use.

--Shane
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kb3ouk
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« Reply #6 on: October 01, 2017, 07:49:51 PM »

So does anyone on here intend on working 630 or 2200 meters or filled out the notification form to the Utilities Technology Council to operate there? I did it on Thursday and haven't heard back yet, I don't have any plans to operate there yet, I wouldn't be able to from my house anyway, but at the far end of the farm is a perfect spot to put up a rather large T antenna and stretch out a nice long Beverage for receive that is good way away from anything noisy, thats what I put down for the coordinates where I would be operating from. Class D rig for 472 khz wouldn't be too hard to put together, if I could get my hands on one an old WW2 navy shipboard MF transmitter would be perfect for down there, considering the average antenna installation would probably need around 150 to 500 watts to make the 5 watt ERP limit.
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N1BCG
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« Reply #7 on: October 01, 2017, 08:21:27 PM »

But actually, the limit is 5 watts ERP.

EIRP, not ERP, an important distinction:

Amateurs operating on 472-479 kHz will be permitted a maximum equivalent isotropically radiated power (EIRP) of 5 W, except in parts of Alaska within 800 kilometers (approximately 496 miles) of Russia, where the maximum would be 1 W EIRP. [EIRP is the product of the power supplied to the antenna and the antenna gain in a given direction, relative to an isotropic antenna (absolute or isotropic gain). EIRP is equal to ERP multiplied by 1.64.]

There are quite a few aeronautical beacons in the 200-400 kHz range running far less than 5 W EIRP at 25-50 Watts TPO with 50' verticals and capacity hats that can be heard hundreds of miles away at night. The potential of the 630M band is significant. Xmtr construction is underway.
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KB2WIG
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« Reply #8 on: October 01, 2017, 09:22:15 PM »



C,

I've got my HP 200C warmed up and ready to go.


klc
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« Reply #9 on: October 02, 2017, 01:37:17 PM »

I sent mine in a couple of weeks back and haven't heard anything back.

Looking around, it appears that the Anan 100D will make some power down there when in extended band mode. I wonder if that applies to the 200D I have as well. If so, then perhaps we'll be able to participate when the curtain goes up.  Grin


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73 de Kevin, WB2EMS
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« Reply #10 on: October 02, 2017, 03:23:50 PM »



I wonder if I can 'run' PSK31 with the HP.Huh

 I'll just winde  a coil atound some  plastic garbage can and load up my 80m di pole.



Klc
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« Reply #11 on: October 02, 2017, 05:06:36 PM »

I hear that can work and have seen some big copper tubing coils on some setups. I'm eyeing some big trees in the back yard with a slingshot thinking of an inverted L. Might be able to get up 60' and then go back several acres...  Probably be good on 160 too.  Grin

Looking at the Anan stuff, looks like the bands may already be in there.   Smiley Going to play around on a dummy load tonight.



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73 de Kevin, WB2EMS
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« Reply #12 on: October 03, 2017, 08:46:53 AM »

Did some checking on the Anan 200D last night and was pleased to find that it already seems to support both bands on receive, though listening around I didn't hear much of anything with my antennas, and in fact not much on LF at all. On 630m I was able to get more than 20 watts output on CW, no output on 2200m. Guess it's time to start looking at the antenna situation.  Smiley

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73 de Kevin, WB2EMS
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« Reply #13 on: October 05, 2017, 10:14:49 PM »

For 630M, I found a simple L network will tune a modest longwire and make a significant difference in reception. Use a BCB oscillator or antenna coil or a loopstick antenna in series between your antenna and receiver. For tuning, connect a 366mmfd (remember those?) BCB tuning cap between the antenna and ground.

Another option is to connect them both in series between the antenna and receiver. This combination should dramatically improve reception across most of the 200-500 kc band.
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WB2EMS
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« Reply #14 on: October 06, 2017, 03:55:07 PM »

I will give that a try Clark. I have a couple of low full wave loops, 80 and 160 meters, and a 40/60 meter dipole and a butternut vertical to play with. And a flaky loop antenna that I don't trust and need to sort out.

I did some listening with the Anan the other night, and didn't find much, even NDB beacons, but it was a brief try. Last night I was playing with Simon Browns sdr-radio version 3 and an RSP1 on the 80 meter loop, and I was able to copy a number of NDBs, including our middle marker at KITH, and I think WWVH down at 60 Khz. Were some buzz saw digital looking signals around 18-25 khz, that might be long wave navy stuff, or could be noisy switchers in the house (though come to think of it, they weren't replicated every harmonic, so maybe real signals) I'll have to check back with the Anan and see if I can get similar results side by side. I may have to figure out how to fiddle the filters in the Anan to pass low signals.

Still scoping the back yard to see what kind of inverted L might be able to go up if I decide I want to try transmitting. The transmit test on the Anan looked promising. Are you listening down there regularly? What are you hearing? In the 472-479 range I saw a couple of weak lines in the waterfall, but nothing that looked like cw. I suspect much of what is there is WSPR, which I'll have to configure on the machine with VAC. Or maybe that's not where the current part 5 activity is. I know I've copied w2zm's station in the past on my TS2000 down around 500 khz, but don't recall the frequency. Where can I look for current activity, and what modes?

Kevin
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73 de Kevin, WB2EMS
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« Reply #15 on: October 06, 2017, 05:29:35 PM »

WG2XSB is regularly on 471 in the evenings from Stowe, MA. I hear it fairly regularly here in SW CT and use it to judge both propagation and the tuning of my L network for 630M reception.
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« Reply #16 on: October 06, 2017, 05:36:46 PM »



FWIW, I registered my location with the overlord.

There is a 30 day review process, no news is good news.


KLC
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« Reply #17 on: October 06, 2017, 10:55:27 PM »

WG2XSB copied tonight on the RSP1 and the 160 meter loop, parts of which are lying on the ground. I'll grab a loopstick and a 365 pf variable, maybe multi section so i can parallel up another and see how they work to tweak the rx. Do they beacon continuously? I am hearing them for a while, then nothing, and then a bit later they are back. I'd fire up the anan but it's getting late and I have an early vet appointment tomorrow for the critters.

Thanks for the info. Are you planning to be qrv on 630 Clark?

Kevin
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73 de Kevin, WB2EMS
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« Reply #18 on: October 07, 2017, 09:31:17 PM »

I ended up giving the anan a try last night after all. Odd results. Running powersdr, latest release, I couldn't hear anything, although using the rsp1 with sdr-radio v3 and the same antenna the station in Stow was good copy. Switching to cusdr, an older version, I was able to copy on the anan, Same hardware and antenna. Go figure.

Kevin, I wonder if we'll be able to work each other.

Off to find out where I put my loopsticks.

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73 de Kevin, WB2EMS
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« Reply #19 on: October 07, 2017, 09:44:16 PM »

A loopstick will work or you can homebrew an inductor. You might only need around 200uH and that's easy to get by winding magnet wire on a toilet paper core. Remember making crystal radio coils? ;-)

WG2XSB coming in well on 471.

Hearing something now on 478kc:

DE WD2XSH / 31 / 31 / 31 K or something like that...

http://w4dex.com/500khz/wd2xsh31.htm


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Steve - K4HX
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« Reply #20 on: October 08, 2017, 12:45:54 AM »

How much power will that loopstick take?
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N1BCG
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« Reply #21 on: October 08, 2017, 01:41:55 AM »

How much power will that loopstick take?

The cap/loopstick combo is for receive only to get a feel for the new 630M band. Coupling power for transmission is going to take something more substantial ;-)
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Steve - K4HX
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« Reply #22 on: October 08, 2017, 12:01:56 PM »

Yep. Litz wire may come back into vogue.
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« Reply #23 on: October 08, 2017, 04:59:50 PM »

The LST-325 probably has a TDE transmitter that will tune around the new freq. and being a good sized ship may have the decent aerial. I know there are hams involved with restoring the transmitters. I've been aboard on a personal tour, very interesting.



If one is in Illinois, why not volunteer to help work on the ship and go all out?
LST-325
http://www.lstmemorial.org/





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kb3ouk
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« Reply #24 on: October 08, 2017, 05:56:51 PM »

A lot of old navy transmitters should be pretty good for down there, the TDE, TAJ, TBL, TCN/TCU, TBW/GO-9, ATD, GP-7, ATC/ART-13 (if you have the LF module), and even the BC-375. I'd like to find the MF unit for the GO-9 to go with the HF unit i have for the same rig.
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