Author Topic: H-Field and E-Field, same enclosure?  (Read 1372 times)

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Offline SLOweather

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H-Field and E-Field, same enclosure?
« on: October 22, 2014, 04:16:09 PM »
Are there any concerns with mounting both amps in and the antennas on the same metal box?

Offline Cutty Sark Sailor

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Re: H-Field and E-Field, same enclosure?
« Reply #1 on: October 22, 2014, 04:40:12 PM »
The E field AMP connects to controller with MINIMUM CAT cable (5, 5e, 6) and connects to the PREAMP with coax. You want less cat cable, so the E Amp should literally mount with a 1' CAT to the 2 input on controller. The Coax is an integral part of the LP filtering for the current design. The E PREAMP would have to mount vertically in an enclosure, with the probe directly connected, extending vertically.  Future development may incorporate a single E/H combo amplifier stage in some fashion, however, using experience gained from the present 'dual system' operation. Should that be implemented, I'd expect both E and H to operate on some similar "preamp" concept, so each can be located in its own separate space.
There might be some possibility of EMI from a nearby H field amplifier. I noted some during a test with the two (E PREAMP and H AMP) close together. (Board to Board induced, not from antennas/probe). I would have low confidence in both AMPLIFIERS or PREAMP next to each other without some fancy metal box, and that could negatively affect both amplifiers. E field Probe wants Air under it, not metal
Also since you're limiting the H antennas and E probe to the same location, height, etc,... this would preclude locating each in its own separate quieter, more 'sensitive' environment.  A good H field environment may not be the best E field location !  (and vice versa).
My E field Probe and Preamp are 22' in the air, on a mast mount, 100' coax to E AMP, which is 1' CAT6 to controller.
My H field Ferrites, Amp, is 40' north, in a "sweet spot" that is about 2m Cubic, (because of my very noisy M environment) with the AMP directly to the antennas, on 50' CAT6 to the controller.  That's its only sweet spot, and mounting the E field in the same location was completely out of the question since that location is inside, 4' above the garage floor.  E field needs to be OUTSIDE and in the air 3-4 meters.

Mike
« Last Edit: October 22, 2014, 04:52:08 PM by Cutty Sark Sailor »
 

Offline miraculon

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Re: H-Field and E-Field, same enclosure?
« Reply #2 on: October 22, 2014, 06:54:02 PM »
I concur with Mike's comments. I would like to add that the wire runs from the mag field antennas to the amplifier need to be kept short. As long as the run between the E-field preamp is longer to both remote it and give the proper capacitive loading, you might be able to put the amplifier boards into the same box.

However, grounding them both to a metal box might create ground loops between the boards and out to the controller. Also, the serial PGA gain communication "talk" might be picked up. I suspect that the signals are ignored during autoranging, but the E-Field might be actively changing gains while the H-Field is listening and vice-versa. I have see this behavior on mine by watching the yellow LEDs when the gains are changed.

So with the amplifier boards away from each other, this won't be an issue. If they are in close proximity, it could be.

If you put a provision in to float one of the boards if needed (nylon hardware comes to mind) and possibly a bulkhead shield between the two amplifier boards it might help.
 
I think that W3DRM "Don" put both amps into his "outhouse" (sorry Don).

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Offline W3DRM

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Re: H-Field and E-Field, same enclosure?
« Reply #3 on: October 23, 2014, 10:36:35 AM »
Nope, my "outhouse" holds both the H-field and E-field antennas. The E-field antenna is directly connected to the E-field Pre-amp which then feeds a 50' coax into my office to the E-field Amplifier board. That board then connects to the Controller via a 5' shielded Cat-5e Ethernet cable. The 5' of cable is soon to be replaced with a 1' section which is currently on order. The H-field antennas (ferrites) connect directly to the H-field Amplifier board which is then fed via 50' of shielded Cat-5e cable into my office and then to the Controller board. My E-field antenna is about 10 to 12 feet off the ground.

I have a single ground from my controller board to my Charter cable modem input line. I see very little change in noise levels with the ground connected or not connected.The E-field antenna is 14" (35cm) in length. Some say 12" is better but this length seems to be working just fine for me. Perhaps when we get more west-coast stations running, I will be able to cut that length down a bit.
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Offline SLOweather

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Re: H-Field and E-Field, same enclosure?
« Reply #4 on: October 23, 2014, 12:20:28 PM »
Well, I do have 2 used steel Hoffman boxes, so I can separate the amps if needed. I already machined up the back plate and installed standoffs for both boards, so I might try 2 in one just for fun. I can also put the E-field amp inside another metal box inside the Hoffman box.

Thanks for all the advice and notes!

Offline Cutty Sark Sailor

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Re: H-Field and E-Field, same enclosure?
« Reply #5 on: October 23, 2014, 01:15:51 PM »
All I could possibly add is that responses from three of the "eldest" and best-looking RED operators have suggested the cookbook be followed...  :roll:
 

Offline SLOweather

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Re: H-Field and E-Field, same enclosure?
« Reply #6 on: October 27, 2014, 12:15:40 PM »
Here's what I had in mind (since the board mounts were already machined before I posted the question).

The ferrites are in a 1/2" PVC assembly based on a corner T. Yesterday I scrounged in the garage and combined a couple of old antennas into one I could mount on a Motorola/NMO mount on the enclosure. The E-field preamp would be right under it. The H-field amp is right under the ferrite assembly.


Offline W3DRM

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Re: H-Field and E-Field, same enclosure?
« Reply #7 on: October 27, 2014, 03:44:11 PM »
Chris,

That's a nice clean looking installation. I don't know if there will be any interaction between the two amps but only time will tell. Are you planning to mount the box on a pole or somehow get it up in the air where the E-field antenna needs to be?

The general consensus is that the E-field antenna and pre-amp need to be elevated at least 10-12 feet off the ground for best results. the higher, the better.
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Offline SLOweather

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Re: H-Field and E-Field, same enclosure?
« Reply #8 on: October 27, 2014, 04:08:11 PM »
Hmmm, I could do that. Easiest would be to not put the E-field antenna/preamp in/on the box, but on a PVC mast bolted to the 6x6 I'm thinking of mounting to... The the enclosure could be down lower. 

Chris,

That's a nice clean looking installation. I don't know if there will be any interaction between the two amps but only time will tell. Are you planning to mount the box on a pole or somehow get it up in the air where the E-field antenna needs to be?

The general consensus is that the E-field antenna and pre-amp need to be elevated at least 10-12 feet off the ground for best results. the higher, the better.

Offline W3DRM

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Re: H-Field and E-Field, same enclosure?
« Reply #9 on: October 27, 2014, 04:29:02 PM »
Getting the E-field antenna and associated pre-amp up higher is the ideal. You then use the RG-6 cable from the pre-amp to the E-field amp that is close to the controller board. Just remember that the leads from the ferrites to the H-field amp must be as short as possible and not twisted together. The ferrite setup you have looks just fine.

One last thing, the length of your whip-antenna appears to be way too long. It should be no longer than 12 inches with 14 inches being the max. The E-field circuitry is extremely sensitive and having too long of an antenna can, and will, cause all kinds of gain control issues. The most important item is the height of the E-field above ground. You simply must get it up in the air and away from the myriad of ground level noises.
Don - W3DRM - Minden, Nevada --- Blitzortung ID: 808 --- FlightRadar24 ID: F-KRNO2
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Offline ke9lz

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Re: H-Field and E-Field, same enclosure?
« Reply #10 on: October 28, 2014, 12:39:39 AM »
I tried to mount both amps in a single box and had trouble with noise.  I opted to mount the controller, E-amp and a wireless router in a plastic outdoor box at the base of my tower, mounted the H-amp (in a outdoor box) antenna combo at 20 feet and the E-antenna about 40 feet to give them some separation on the tower.  So far knock on wood it has worked fine and have not had much problem with noise.  We finally had some storms close in today and I was able to do some more fine tuning =D>.

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