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 Post subject: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Feb Sun 25, 2018 3:59 pm 
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Location: Jefferson, WI 53549
Hi,
I plan on building and installing a longwire antenna for use in picking up shortwave signals on some of my WWII Military equipment. I understand the fundamentals of it, but I have a question about the ground. Most examples I have seen run a separate copper line to a separate ground rod driven into the earth. I have a tall TV tower already on the property right next to my radio shack room. which is where I will start the longwire antenna from. Could I ground to that rather than driving in a new ground rod? Would that be adequate, am I missing something here? Is there something better I could used rather than a longwire? I'll be hooking it into a BC-348 (200-500 Kc 1 band 1.5-18.0 Mc 5 bands), and a BC-654 (3.8 – 5.8 Mc Bands)

One example showed grounding the ground lug from the radio to the ground on the house outlet? Wouldn't you get a lot of noise with that?

I'd also like to use coax running from radio with a BNC connector to the longwire antenna, I was thinking of using RFC240 coax, the run from receiver to antenna would be about 15'. Or should I just use 14 gauge wire like the long wire antenna itself?


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Carl Reinemann
1953 Dodge M37 &M101 Trailer
WWII Crosley SCR-284
Assorted WWII military radios


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Feb Sun 25, 2018 4:57 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1128
Location: Champaign IL 61822
There have been plenty of responses to this same question in this forum
in the past six months ... look at the back topics.

That said ... the key, in the modern world, is reduction of noise, not really increase
of signal. Your plan will work great IF you have a great ground system, and
connect your feedline (coax) directly to it with zero lead length. If this is near
the house, or power lines, the antenna can pick it up from them too.

My my lesson: you can't assume that any particular antenna design will
work well for you, as you have a unique situation. You have to experiment!

Consider a Beverage antenna, even if too short and lying on the grass. That worked
for me.


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Feb Mon 26, 2018 3:57 am 
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Joined: Sep Thu 01, 2016 3:56 am
Posts: 208
Location: San Jose, Ca.
Grounding is an interesting issue. The state building codes require only one earth ground per building, and that is usually where the meter is at. That is purely a safety issue. However, we know that sometimes certain antennae require a ground, like a 1/4 wave vertical. That's another story.
The wall outlet ground should be good for your scenario, as long as it is a good RF ground. It probably is not, unless your rx is next to the main power input to your home. A good RF ground will help in minimizing noise getting into your rx. If you need to improve the RF ground at your rx, You can run a copper braid from it to the main power input ground. Your tv tower if not grounded to the main, should be because it's close to your home. So, if it is grounded properly, then yes you can use it for a ground.

As mentioned already, minimizing noise to the input to your rx is a very good idea. A beverage antenna (as mentioned) is good for that. In any case using coax from your rx to the antenna is a big help in minimizing house noise from getting into your rx. The key is correct grounding of the coax ends. If you ground both ends, you are probably inducing noise into the shield and thus your rx, unless both ends are on very good RF grounds of equal potential. That's difficult to do, so ground the end at the rx and leave the other end ungrounded.

Because your tower is metal, try to keep the active parts of your antenna at least 5' from it, 10' would be better.

As you know, coax is low impedance and your long wire probably won't be. There are matching transformers you can use, but I have found that they are not always necessary or beneficial. As mentioned before, you may need to experiment.

Regards, Larry


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Feb Mon 26, 2018 6:03 am 
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Joined: Sep Thu 01, 2016 3:56 am
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Location: San Jose, Ca.
I forgot to mention that water pipes can provide a fair ground for receivers. Galvanized can be OK and copper is mush better, but may not be good enough either. You can try them if you have access. I'd suggest testing them if you're going to use them. You'll need to temporarily run a solid copper wire from the earth ground at your meter to the prospective point and measure the resistance and a/c voltage between the two. If you get more than a couple ohms or any voltage, something is wrong. Don't use that spot.

Regards, Larry


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Feb Mon 26, 2018 3:27 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1128
Location: Champaign IL 61822
I have found that the critical point is proper grounding, which in my case means
NO DIRECT CONNECTION of the antenna to the house ground system.
The coax from the receiver goes out to the antenna. It is connected to the antenna
with a low capacitance (5 pF) transformer. There is no DC connection at the
antenna end: the coax is NOT GROUNDED ... this is ultra-critical. As I mentioned before
the connection to the coax, i.e. the transformer, is right at ground level, a very short lead.

This seems to work well with a resonant antenna with a 1:1 transformer. If the antenna is not resonant
for best signal transfer you would need a transformer with a different turns ratio or,
as I use, a BATTERY POWERED preamp with a 50 ohm output (feeding the transformer).

To get rid of noise you nave to be creative and COMPLETELY FORGET "codes" not designed
for minimum antenna noise pickup.


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Feb Mon 26, 2018 3:47 pm 
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Location: Jefferson, WI 53549
Thanks for all the tips,

Just to be clear, on the coax run to the long wire, ONLY the shield is grounded at the RX but NOT at the antenna end, correct?

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1953 Dodge M37 &M101 Trailer
WWII Crosley SCR-284
Assorted WWII military radios


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Feb Mon 26, 2018 5:59 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1128
Location: Champaign IL 61822
creinemann wrote:
Thanks for all the tips,

Just to be clear, on the coax run to the long wire, ONLY the shield is grounded at the RX but NOT at the antenna end, correct?


That's true in my setup. The problem is, every problem is different, your setup
might need the opposite.

That's the difficulty with receiving that does not apply to transmitting. Transmitting
is about getting power out efficiently. To do that you must get at least reasonably
far away from both random highly conductive things and medium conductance things like the
ground. You don't have to worry about noise.

With shortwave receive, there is always noise around, even if only atmospheric.
So the goal is to get the highest S/N ratio. The presence of other things, if they
are not transmitting noise, is quite OK. Inefficiencies are OK if they help the S/N.
The Beverage antenna is the classic example.


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Feb Mon 26, 2018 10:39 pm 
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Joined: Sep Thu 01, 2016 3:56 am
Posts: 208
Location: San Jose, Ca.
My apologies for not being clear. When I was talking about improved RF grounding, I was referring to the rx. And, I did say that the antenna end of the coax shield should not be grounded or it will normally induce noise into the shield.

Regards, Larry


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Thu 01, 2018 5:17 pm 
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Location: Jefferson, WI 53549
Thanks everyone!

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1953 Dodge M37 &M101 Trailer
WWII Crosley SCR-284
Assorted WWII military radios


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Thu 01, 2018 8:14 pm 
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Quote:
I have found that the critical point is proper grounding, which in my case means
NO DIRECT CONNECTION of the antenna to the house ground system.


Wait for the firestorm to start. Where's all the "doesn't comply with NEC regulations" guys gone..... :)

I don't comply, I have a buried 6' copper plated rod outside my window that all the radio grounds go to.

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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Sat 03, 2018 8:04 pm 
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Location: Warner Robins, GA
majoco wrote:
Quote:
I have found that the critical point is proper grounding, which in my case means
NO DIRECT CONNECTION of the antenna to the house ground system.


Wait for the firestorm to start. Where's all the "doesn't comply with NEC regulations" guys gone..... :)

I don't comply, I have a buried 6' copper plated rod outside my window that all the radio grounds go to.


For my R-390 I ran a piece of copper braid from the chassis to the ground rod at the meter.

I have a power strip that has an indicator light that comes on when there is a ground and it is missing the ground pin. The R-390 is plugged into it with a grounded cord. I have a nifty indicator of how good the ground is.


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Sat 03, 2018 9:42 pm 
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Joined: Apr Thu 12, 2007 3:24 am
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Location: Milwaukee,WI
I have a tower along side the back of my house with its own ground rod separate from the electrical service ground rod. The 2 rods are about 15 feet apart and in clay soil. After reading posts here about electrical code I'm now curious to measure the AC voltage and/or resistance between them. But, all of my antennas on the tower have no electrical connection to the tower. So the only grounding that happens is when I screw the coax on the back of a boatanchor radio that uses a 3 prong power cord. So if there was some differential voltage between the 2 outside grounds I'm pretty safe from it since no coax shield is connecting between them.


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Sat 03, 2018 10:47 pm 
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Joined: Sep Thu 01, 2016 3:56 am
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forumuser, That's a good installation. It's electrically safe and in compliance with electrical codes.

Regards, Larry


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Tue 06, 2018 3:27 am 
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Location: Central PA 16801
read about my antenna system here:

viewtopic.php?f=1&t=336818

here:

viewtopic.php?f=10&t=284409&hilit=Antenna&start=0

and here:

/viewtopic.php?f=2&t=243014&start=0

steve

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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Tue 06, 2018 5:23 am 
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Joined: Sep Thu 01, 2016 3:56 am
Posts: 208
Location: San Jose, Ca.
Steve, Nice long wire. Sounds like it works quite well. I read through all your postings you pointed to and just had a couple questions:

1. Is your ling wire terminated in any way?
2. How high is it? I know you said it started at your roof eve.
3. Did you try it without your large ground field and with just a small one next to your home instead?

Regards, Larry


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Tue 06, 2018 4:58 pm 
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Location: Worcester Massachusetts
I am amazed at how antennas have now become this "pseudo-science", especially on YouTube, where everyone thinks they know THE way to string up an antenna, or will want to know every minute detail as to "what are you running"? Personally, I find having a proper ground to be a good thing, and there are certain receivers that I have, such as the S-38, and SX-42, that really do seem to benefit from it. Oddly, it seems online that people want to know THE perfect antenna installation, as opposed to simple experimentation. Don't be afraid to experiment. If the "perfect" antenna existed, which it does not, why would you get so many ideas and opinions?

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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Tue 06, 2018 6:27 pm 
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Well put Arthur! The antenna is dependent upon its environment and every environment is different (coupling of other objects to the antenna, source/direction/intensity of local noise sources, coupling/interface to the receiver, directional characteristics of the antenna, favored frequency ranges/distances/operating times, etc.).

A lot of this "perfect antenna" business had its genesis when EZNEC and other similar programs became popular and many users missed the distinction between model and model purporting to represent reality. These modeling programs do an excellent job of modeling how a particular array behaves based upon the assumptions of the model but in many cases the surrounding environment is either largely ignored or very imperfectly included within the model.

This doesn't mean that these modeling programs aren't very useful because they are however the "perfect" setup spit out through modeling likely won't be as perfect in your real world operation.

It is the radio version of "bench racing" :)

Rodger WQ9E


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Tue 06, 2018 6:51 pm 
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Lately, I am seeing folks on YouTube trying Wellbrook Loops? I think that is what they are called. To me, the critical component now in antennas is the constriction of feeds, so as to prevent RFI/noise. I don't think sensitivity is as big of a deal- pretty hard, short of an alligator clip lead, to construct an antenna that does not yield a good amount of sensitivity. I am sure people that have these loops do love them, although the prices do seem a bit exorbitant for what they are.

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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Tue 06, 2018 7:07 pm 
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I am spoiled living in a quiet rural environment where I don't have to deal with noise generation by others and it is pretty easy to keep local RFI under control but I can certainly understand that RFI pickup has become the primary concern of many listeners. I believe it was in 1999 or 2000 when my college moved from its old home which had been originally built as the university library during the 1930s to its newly constructed building and that move meant going from a building with minimal wiring infrastructure to a modern purpose built building with all of its modern noise generators and after that move having any sort of radio in the office (including FM broadcast) was useless.

There are so many noise generators out there now that even if stringent regulations were enacted it would be over a decade before there is any relief and there is no impetus for such regulations. Unless someone successfully creates a "health scare" over all of the radiated garbage things will continue to decline since there is not enough interest in radio reception to result in changes.

Rodger WQ9E


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 Post subject: Re: Longwire antenna and Radio Receiver Grounding questions
PostPosted: Mar Tue 06, 2018 8:03 pm 
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creinemann hasn't responded in a week...

IMHO using coax as a "shielded wire" without the benefit of baluns at either end will result in a vertical run that will attenuate the incoming signal as well as still make the downlead vulnerable to local noises... There will be some entrance of the vertical component of the signal too.

The O.P'.s desire to eliminate noise intrusion will have to include baluns of some form at least at the antenna end. The type of the balun determined by the design of the antenna. A single wire will not match well...

This was an experiment I went through a long time ago and tried to avoid the use of baluns. Too expensive for my allowance... The antenna did not perform well...

IMHO: creinemann should look at what the receiver's input impedance is, even a reasonable guess and if it is balanced or single ended. Then look at what bands of specific interest are desired. Only then choose an antenna type that can support a "transmission" line that appeases both the antenna and the receiver with or without the use of balun(s).

Those choices above coupled with the installation of a short direct to earth ground system should maximize the performance of the antenna with the least noise.

There may be hidden challenges, if the receiver is the "hot" chassis type or the desire to have a very broad band antenna.

YMMV

Chas


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