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Receive Antennas (below 30MHz) - For all topics related to receive antennas used on HF, MW, LW, etc. For transmit antennas use the Amateur Radio Antennas forum.

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Old 12-06-2018, 5:41 PM
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Default Basic Receive Only Long-Wire Ant. Questions

Hello,

This is one subject that has always confused me.
My fault, as I have not put any real amount of time into studying it, like I should.

Let me please ask the following:

a. For a receive only antenna for <30 MHz:
A simple long-wire Horizontal antenna.

If i want, e.g., to optimize reception from a station in London (I'm in Boston), do I want to point the axis of
the antenna toward London, or should the wire (axis) be 90 degrees to the Boston-London axis ?

b. Hard for me to string up outside now.

If i run it around 3 walls of my study, e.g., do the changes in direction adversely effect reception to any degree ?
Would it be better to run around only 2 walls, and accept a shorter overall length ?

Or just a straight, short run (the room dimension only for the overall length now) with no changes of direction ? [shortest length, but no directional changes]

if anyone might explain the tradeoffs here, would be most appreciative.

Thanks,
Bob
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Old 12-06-2018, 5:55 PM
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Basically, a horizontal random wire antenna will favor reception perpendicular to its axis.
An indoor antenna may pick up more noise than signal. You will have to experiment.
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Old 12-06-2018, 6:14 PM
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The answer depends on the frequency and length of the antenna. For example, if you had a 100ft long wire and your target frequency was around 5MHz, the antenna would work best broadside to London. That same 100ft wire at 10Mhz would have a clover leaf pattern and would pick up best at about 45deg to broadside. The same 100ft wire at 20MHz would have an 8 lobed pattern and so on.

Wrapping the wire around the house can help or hurt the pattern, again depending on frequency and length of wire. I can go into more detail if you want on frequency vs length stuff.

Edit: here is some info on patterns vs wire length. You can calculate your target frequency into half wavelengths by dividing the frequency by 468 to give you the length in feet, then multiply by the number of half wavelengths to get the pattern you want. Antennas for the HF band that are low to the ground will have a very distorted pattern that predominantly points up anyway.

https://www.quora.com/How-do-the-rad...of-the-antenna

Last edited by prcguy; 12-06-2018 at 6:23 PM..
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Old 12-06-2018, 8:19 PM
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The other elephant in the room is what is the radio being used?

As recounted in many messages, hanging a long random wire on a portable is usually a no-no. In Boston, with the 50kw clears and myriad of AM and FM towers scattered about and 1 hop from Sackville, that may be a issue to be dealt with. If a portable radio, I wouldn't use anything more than a 30 foot wire (no directionality to worry about) to start with.

If attempting to listen to the BBC transmitters in England, as the NA services are no more I assume the weaker rear lobes of beams to parts of Af/ME/As would have to be sought out.
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Old 12-06-2018, 9:54 PM
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Quote:
Originally Posted by w2xq View Post
The other elephant in the room is what is the radio being used?

As recounted in many messages, hanging a long random wire on a portable is usually a no-no. In Boston, with the 50kw clears and myriad of AM and FM towers scattered about and 1 hop from Sackville, that may be a issue to be dealt with. If a portable radio, I wouldn't use anything more than a 30 foot wire (no directionality to worry about) to start with.

If attempting to listen to the BBC transmitters in England, as the NA services are no more I assume the weaker rear lobes of beams to parts of Af/ME/As would have to be sought out.
Good question. I went round and round with a guys HF interference problem until I realized he was using a cheap SDR dongle without any sort of preselection. I showed him a site selling preselectors for SDR and they had a waterfall image just like his as a before picture.
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Old 12-06-2018, 9:59 PM
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If memory serves, you are using a WinRadio. Don't skimp on the antenna. A poor antenna on a very good radio is only going to provide rather poor results.

One of the big issues you will run into with indoor antennas - which are always inferior to a good outdoor antenna - is noise pickup, especially from your PC or peripherals.. Fortunately that's something that loops reject pretty well. Even if you can't afford a full blown LVP loop, how about his experimenter's kit - which is a lot less expensive? Granted that the loop will be compromised somewhat, but it should still work better than a wire.

How are you with building? Can you solder and use small power hand tools? Then maybe the Carpet Loop is a good choice, particularly if you have a good junk box. I used it on my TenTec RX320D in my condo, and it worked surprisingly well. Certainly better than a wire thrown across a room.

How about what I like to call the MacGyver special?

In fact it can be an advantage to have more than one type of antenna available. What isn't coming in well on one antenna might come in on another. Here are the relevant links...

Loops - The RadioReference Wiki

The McGyver(tm) special - The RadioReference Wiki

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Old 12-06-2018, 10:22 PM
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Quote:
Originally Posted by w2xq View Post

If attempting to listen to the BBC transmitters in England, as the NA services are no more I assume the weaker rear lobes of beams to parts of Af/ME/As would have to be sought out.
Good observation.
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Old 12-07-2018, 12:59 AM
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Quote:
Originally Posted by RFI-EMI-GUY View Post
Good question. I went round and round with a guys HF interference problem until I realized he was using a cheap SDR dongle without any sort of preselection. I showed him a site selling preselectors for SDR and they had a waterfall image just like his as a before picture.
Unfortunately there are a few SDR receivers on the on the web that exhibit image problems. One in the New England area had the 49m Cubans also appearing in the upper end of the 40m phone band. T'was impossible to figure out what was real. When i tested portables for RNMW, one of my checks was to look for nighttime 49m Sackville signals plus-or-minus the IF. Dead giveaway on strong signal handling.

Thus my elephant in the roon comment.
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Old 12-07-2018, 3:29 AM
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Below 100 feet or so a wire antenna won't be that very directional on SW, or MW for that matter. So run it wherever you can. At some of the higher SW frequencies there may be additional reception off the sides of the wire, but directionality doesn't really kick in on SW until you go longer than 50-100 feet, depending on target frequency.

If it's an indoor antenna, putting it in an L or other configuration won't harm the reception. But like others here said, you may get more RFI from an indoor antenna than you will if you have it outside. The plus, of course, is you'll get less chance of static zapping your receiver's RF circuits and frying them.

If the OP is aiming for MW reception from Europe (instead of SW), a decent sized tuned loop is highly suggested.
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Old 12-07-2018, 7:18 AM
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Default From OP:

Hi All,

Just a quick thanks for everyone's comments and suggestions.

Have learned so much over the years from the folks here.
Great RR forum(s) and folks.

Just for info.:

In my Study, I have a new SDRPlay RSP-2, and i use it with the various SDR programs
on my Mac. Lots of fun. Fairly good outdoor antenna for the HF, and a Scantenna in the Attic.
Decent setups, probably.

Also have a fairly old Excalibur, but the only way i can use it is with Bootcamp on the Mac.
A real pain switching. Won't work via Parallels (confirmed by WinRadio).

This question was with regard to a new C Crane Skwave (with SSB) that i bought
to play around with in my bedroom, No Mac or SDR there.
Antenna for would have to be indoors, around the room somehow.

Thanks again,
Bob
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Old 12-07-2018, 12:04 PM
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The Carpet Loop should work just fine...certainly better than a wire thrown across a room...Mike
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Old 12-08-2018, 6:23 PM
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Default Which Antenna setup Best For C. Crane Skywave ?

Hello,

This is a bit of a follow on to my previous Post, but I imagine
Itís different enough to warrant a new Post. Donít want to violate
any forum protocols.

Have a new C. Crane Skywave (SSB) radio.
Quite impressive, but itís obvious to me now that using it inside the house
results in poor, very, reception. Undoubtedly due to all the pc and gadget generated RF

So, I will try to implement some kind of outside antenna.

Very weak in antenna knowledge/theory, so please put up with my
very basic questions, please.

The radio apparently uses a ferrite coil antenna built into the case for
the broadcast band, and an extensible telescopic antenna for everything else such as HF, VHF, aero, etc. This is what I would expect it should be.

But-

Pretty cold out there now, so I canít really experiment any.
But I can, probably do (a) or (b) below.
Would appreciate thoughts on which would be better as an overall
compromise for all bands the radio is capable of.

They say to clip the Reel antenna that comes with the radio to the end of the telescopic whip. It is 23 feet long, and has a clip for this purpose.

I would think that this would be a good setup for HF frequencies only, below 30 MHz or so, and not the way to go for anything higher.
For higher frequencies, I am used to using an antenna like a Scantenna or a discone.

What am I missing here ?

Also, they say there is a built in capacitor in this wire reel.
What does the capacitor do ? How necessary is it ?
Which end would it be on; clip end or reel case end ? Does it matter ?

a. So, I can just run this reel antenna out he window to a tree
20 feet or so away. The reel case would be by the tree.
Would this, therefore work well for frequencies above 30 MHz ?
Apparently yes, but I donít understand how.

b. Or, would it be better to just run a simple single long wire
from the radio to a different tree, but, 35 feet away (15 feet further) ?

Would this work (better) for >35MHz ?

There would not be any capacitor in this setup.

Please educate me a little.

And, should I implement (a) or (b), orÖ?

Most appreciative for your help and time, thanks,
Bob
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Old 12-08-2018, 9:16 PM
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The answers will not differ greatly from this thread, frankly...particularly since I don't believe that radio has an external antenna jack...

https://forums.radioreference.com/re...questions.html

I strongly suspect the cap in that reel antenna is there to drain off static charges. One zap of static electricity and one or more stages in that radio would undoubtedly go dead, rendering the radio deaf as a post on one or more bands.

That lack of an antenna jack really limits your options, and I suspect you would have done better with a Tecsun PL-660, but it is what it is. You might even do better wrapping wire around the perimeter of a nearby wall away a few times. It's an old trick, kinda tacky, but it just might work especially if you use the first timer project I gave in another thread so you can control the gain to avoid overloading issues.

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Old 12-08-2018, 9:43 PM
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Quote:
Originally Posted by ka3jjz View Post
The answers will not differ greatly from this thread, frankly...particularly since I don't believe that radio has an external antenna jack...

https://forums.radioreference.com/re...questions.html

Mike
^^^^ What he said. With all due respect I would suggest you are overthinking the matter.

The "reel" windup antenna is typically something that csn be quickly hung up, and then put away. I often used one when in a hotel room to gather HF signals from the nearby window in otherwise a concrete-and-steel box. It could be quickly wound up the next morning, put away before housekeeping ventured in.
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Old 12-08-2018, 10:49 PM
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Really? No antenna jack? That's definitely a minus point. I hook my Tecsun PL600 to a screw-head in an aluminium window frame right next to my bedside table - works a treat except when it rains!
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Old 12-09-2018, 12:03 AM
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Quote:
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Really? No antenna jack? That's definitely a minus point. I hook my Tecsun PL600 to a screw-head in an aluminium window frame right next to my bedside table - works a treat except when it rains!
Not here Marty-they're bonded to the building!
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Old 12-09-2018, 3:49 AM
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Ah, but my building has 2 x 4 inch wooden framework covered with a 3 inch thick veneer of stone and plaster - no electrical bonding in the structure, only in the wiring and the water pipes! The first house I bought in 1974 was with a government loan and I was surprised to see that it's expected life was 35 years - I was happy to see it was still there a couple of weeks ago!
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Old 12-09-2018, 6:28 AM
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SiLabs DSP chipped SW radios probably do not need much of an antenna for most SWBC purposes, hence the lack of an external antenna jack on many of the models.

My Grundig G2 (which has a SiLabs DSP chip) has only the whip, and even with the whip reduced by a couple inches it will pick up nearly every single SWBC station my Sangean 909 will get off a 25-30 ft wire, albeit at reduced levels (and in many cases, reduced quality). That's reception off a 6-10 inch whip vs. reception off 25-30 ft. of wire (two stories up in a wooden building).
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Old 12-09-2018, 7:25 AM
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Default From OP: Multiple Loops ? And, Re Simple Long Wire For VHF ?

Hi All,

Thanks for help with this.

Will have to dig out my (very) old books on antenna theory and try to get into again.
Interesting subject, as it always seems to combine "theory" and a bit of black magic.

Appreciate the help, very much.

Regarding running a simple wire around the 4 walls at the ceiling of my room:

Is there anything likely to be gained by doing it a few times (multiple loops) ?

And, my previous question re how a simple long wire can be used for vhf and stuff >30 MHz ?
Any thoughts and wisdom on this ?

Thanks,
Bob
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Old 12-09-2018, 9:26 AM
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Bob this forum is for 30 Mhz and below. Please ask your questions about antennas for frequencies above 30 Mhz elsewhere.

However the question is moot. As you have no external antenna jack on that radio (I think), there's little you can do about adding an antenna for VHF Air or FM

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