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Author Topic: 630 Meter Reception - Start Cheap and Simple  (Read 5127 times)
AE5X
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Posts: 1029




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« Reply #15 on: October 31, 2017, 01:36:08 PM »

Can't wait to learn what you're using.

Here's a short write-up and photos of my cheap and simple set-up. Thanks K0OD for your WSPR reports  Smiley

http://ae5x.blogspot.com/2017/10/first-transmissions-on-630-meters-at.html
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KM1H
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Posts: 2614




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« Reply #16 on: October 31, 2017, 02:18:32 PM »

Maybe you are living on the mother lode of excellent ground conductivity and the loss is in the coil.



From AA2UK:
Quote
I thought I'd add that many stations on 630 meters are using active E Probe antennas. They are usually placed anywhere from a few feet off the ground to 30'. I'm learning many of the RF principals we have learned about HF don't apply to LF/MF.

Clarify that Bill as it may be misleading to some.

Carl
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KD8IIC
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Posts: 668




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« Reply #17 on: October 31, 2017, 06:14:27 PM »

  Funny how some of the pros here who have never even used an E probe or an active shielded loop can be so positive with their speculation that they don't/won't work well for this application.
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K0OD
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Posts: 2985




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« Reply #18 on: October 31, 2017, 10:15:05 PM »

From the descriptions I have seen of "e-probe" antennas, they tend to simply be a shortened vertical with poor ground planes and usually a receiver preamplifier to make up for their poor gain.

The e-probe and h-probe concepts are generally totally misleading as they relate to antennas. Is there really anything new here?...

- Glenn W9IQ

Yes, there's something new. They used to be called "Active Antennas" by the marketing guys until a newer marketing guy came up with "E-Probe."

Maybe I'll start calling my 43' vertical a "Collinearized I Probe." "It enables copying signals you can't even hear with ordinary antennas."

Add 6dB if your 43' aluminum stick is a Zero Five rather than a cheaper brand aluminum stick. (remember the ridiculous performance claims made by ZF users early on)

For us old geezers....




« Last Edit: October 31, 2017, 10:29:04 PM by K0OD » Logged
KM1H
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Posts: 2614




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« Reply #19 on: November 01, 2017, 03:20:11 PM »

 
Quote
Funny how some of the pros here who have never even used an E probe or an active shielded loop can be so positive with their speculation that they don't/won't work well for this application.

Ive been using a balanced two turn shielded loop made from 1" CATV cable since about 1984. It contains a remotely tuned preamp using PP U-310 Jfets, is about 250' back from any homes, is rotatable and the bottom is about 8' high, diameter is 40" iffn I remember. Covers BCB thru a bit above 160M. It gets used when the Beverages are too noisy.

I should build another for 630M and compare to those same Beverages.

Carl
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W4AMP
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Posts: 28




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« Reply #20 on: November 29, 2017, 07:50:02 PM »

Tried receiving 630 and 2200 meters on a 160 inverted vee with poor results. Just installed a L400B active antenna and it receives much better. Have it hooked to my receive antenna jack. I know I have to hear them before I can work them. Did not hear back from UTC so legal to transmit. Doubt it is worth modifying my FT5000 for a few milliwatts of transmit, will cobble up a transmitter eventually.
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AA2UK
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« Reply #21 on: December 03, 2017, 04:37:24 AM »

Tried receiving 630 and 2200 meters on a 160 inverted vee with poor results. Just installed a L400B active antenna and it receives much better. Have it hooked to my receive antenna jack. I know I have to hear them before I can work them. Did not hear back from UTC so legal to transmit. Doubt it is worth modifying my FT5000 for a few milliwatts of transmit, will cobble up a transmitter eventually.
The FT5000 might be worth converting if you use an amplifier with it. Digital modes like JT9 seem to be the majority of 2 way Q's made on 630. You might need +10-15dbm to drive some of the class D amps used.
73, Bill
AA2UK
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K0OD
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« Reply #22 on: December 03, 2017, 06:41:10 AM »

Is there a JT9 calling frequency in common use?

Quote
"Just installed a L400B active antenna and it receives much better."

We'll see. I ordered one yesterday. The LF Engineering L400B probe combines a low pass filter and a small active antenna. Unlike similar antennas it only works below about 530 kHz. Will power it with batteries.
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AA2UK
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« Reply #23 on: December 03, 2017, 07:39:37 AM »

Is there a JT9 calling frequency in common use?

Quote
"Just installed a L400B active antenna and it receives much better."

We'll see. I ordered one yesterday. The LF Engineering L400B probe combines a low pass filter and a small active antenna. Unlike similar antennas it only works below about 530 kHz. Will power it with batteries.
It's not really needed most of the Op's use the WSPR freq being 474.2kCs (1400-1600hz) as the band center, then JT9 is down 100hz (1300-500hz) Audio freqs. This allows looking at the WSPR signals and observing most of the JT9 activity using the slow graph in WSJTX. Once you see a signal below the WSPR range just change the decode mode in WSJTX to JT9.
That's what I have observed from here...
Bill, AA2UK
« Last Edit: December 03, 2017, 07:43:03 AM by AA2UK » Logged
AA2UK
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Posts: 371




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« Reply #24 on: December 03, 2017, 07:44:37 AM »

GOTHAM, every 9 year old ham's version of a "wet dream".
Bill, AA2UK
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AE5X
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Posts: 1029




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« Reply #25 on: December 03, 2017, 08:01:00 AM »

Is there a JT9 calling frequency in common use?

Quote
"Just installed a L400B active antenna and it receives much better."

We'll see. I ordered one yesterday. The LF Engineering L400B probe combines a low pass filter and a small active antenna. Unlike similar antennas it only works below about 530 kHz. Will power it with batteries.

What antenna have you been using? I'm looking forward to reading your impressions of the L400B.

630m band plan:
http://njdtechnologies.net/what-happens-where-on-630-meters-a-few-more-comments-about-where-to-place-your-signal-depending-on-mode/
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K0OD
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« Reply #26 on: December 04, 2017, 05:06:00 AM »

John, I use my DXE 43' vertical for 630 meter reception. Still don't have a way to transmit there. The e-probe should arrive soon and I'll compare the two antennas in detail. 
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N0YXB
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Posts: 1140




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« Reply #27 on: December 04, 2017, 09:10:23 AM »

The e-probe should arrive soon and I'll compare the two antennas in detail. 

Thank you, I'm very curious about e-probe performance at these frequencies, especially in a suburban setting.
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K0OD
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Posts: 2985




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« Reply #28 on: December 04, 2017, 11:28:24 AM »

Vince, I see that you live in the Saint Louis area. I'm in Town and Country. My  antenna is about 100' off Topping Road, and 30' behind my house. 

Actually you can sorta compare my 43' vertical with an E-Probe now using WSPRnet.  KA9CFD in Colchester Il does fabulously with the same probe I'm getting. He's often connected to that site and so am I, weather permitting. "SWL/K9" uses a e-probe too and he's often listed. Both guys hear better than I unless they're encountering high local noise. From what I can tell from WSPRnet, both can hear stations that are generally about 3 dB to 7 dB weaker than what I can decode. My reception is better  only about 5%-10% of the time, maybe due to storms up their way. 

Is their advantage because they use probes or is it because both are in very rural areas?  On 630m rural locations generally offer two receiving advantages... lower local noise and less crud from nearby AM broadcasters.
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K5DN
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Posts: 25




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« Reply #29 on: December 04, 2017, 04:36:18 PM »

One thing to watch out for with E-probes (active antennas) is that many design have no common mode isolation at the base of the antenna.  And that apparently  includes the L400B.  In my experience, particularly in a suburban envirnonment, much of the noise I was picking up was conducted from the equipment ground in the house, through the coax shield, and right into the antenna.  Adding an adequate common mode choke helped a lot.

And a few turns of coax over some ferrite won't do it.  There are commercial common mode chokes that will do it; or a bifilar winding on a ferrite torroid or binocular core could do it; but you need several K-ohms of reactance to do any good.  A signal isolation transformer will also work, but you need to feed the supply current around it with dc chokes (two; one supply, one ground).

I haven't tried it, but there are published designs using no amplifiers at all; just a step down isolation transformer at the antenna and another in the shack.  I think it could work well.

Bob
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