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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 02-02-2011, 9:12 PM
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Default How do I make a HF Long Wire antenna?

I am trying to get better reception on my TH-F6 for HF and shortwave frequencies. I have had handheld receivers and transceivers that cover the HF and SW frequency spectrum for some time but have never actually heard any broadcasts and I know this is due to inadequate antennas. I have never had an HF antenna. I know I am not going to hear anything on these radios with the standard rubber duck antennas.... I would like to build a long wire antenna. My question is how do I accomplish this... I have seen several sites on longwire antenna construction but none really address how the wire is connected to the radio. This may be common knowledge to people that build antennas but here is what I am trying.

1. 18 ga wire
2. bnc to motorola male plug adapter
3. solder iron

If I run a length of wire soldered to the motorola male plug tip will this need to be grounded to get reception (if so grounded to what)? OR will this be enough to get a signal?

Excuse my ineptness in this subject. I am just getting into the antenna field of this hobby and I am a bit uneducated as of yet. Any sites that explain how to make antennas or antenna theory that are not using calculus to explain the theory?
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Old 02-02-2011, 9:44 PM
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Though the TH-F6a has the ability to receive HF-connecting a large outdoor antenna is not recommended due to severe front-end overload. If you decide to build a longwire you will need to ground it due to static build up and discharge on the wire.

If you want something simple that wont heavily overload the receiver take some RG-8 mini, expose one end as if youre soldering a connector but seperate the twist braid and center conductor. Then solder an 8 foot long piece of wire to the center conductor and another 8 foot piece of wire to the twist braid. At the opposite ends of each wire create a loop or attach to ceramic or plastic dog bone insulators and hang from opposite walls in a bedroom or attic. You have just made yourself a dipole.

If you want something even more simple, use a wideband scanner antenna like the Radio Shack discone or mobile mag mount. Ive had moderate success with both.
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Old 02-02-2011, 9:46 PM
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String your wire up, outside if possible and enjoy. A ground really isn't necessary and will maybe add a marginal difference.
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Old 02-02-2011, 9:48 PM
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You really don't want to put a 'long wire' on a handheld, as it will very badly overload it (a true 'long wire' is one or more wavelengths long at a given frequency - it would never handle that kind of signal input. Overloading is almost assured...)

I would say soldering about 5-10 foot (maybe no more than 20 foot or so) onto the pin of a BNC would do the job. No grounding needed. The total length would depend on where you are in the US (West Coast sigs tend to be a good deal weaker than listening on the East Coast) and the freqs involved. But wherever you are, don't put a lot of wire on it. It's simply not designed to handle it.

Another possibility would be an extendable whip. However, be careful with this - fully extended it puts a LOT of strain on the BNC connector in the radio. Don't walk around with it fully extended.

best regards..Mike
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Old 02-02-2011, 9:57 PM
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Default Longwire

Any random length of wire will be adequate to pick up broadcasts. You would not need to ground a random length long wire. For ham radio the common rule of thumb for a random length long wire was at least 32-36 feet for a tuner to work with it for all bands with good results. If you know the specific band you would like to use you can get more gain if you trim it to the wave length of the frequency you want to use it on. 234 divided by frequency is the formula for 1/4 wave length for practicle antenna use (234/f). So if you wanted to listen mainly around 5MHz you are looking around 45 feet. You can make a dipole with RG 58 or RG 8x using the above formula with a BNC connector. Just trim the insulation on the end of the coax and solder 30 to 40 feet of wire to the center conductor ond another 30 to 40 feet to the shield. Wrap it up in elecrical tape so you dont get water down your coax and you are set.
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Old 02-02-2011, 10:25 PM
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Thanks for the quick replys. So is the hf and shortwave functionality in wideband receivers and transceivers just for spec sheets and has no functionality? I have always wanted to listen to hf ham bands and figured the kenwood th-f6 would be a good choice for this since it allows usb and lsb... I have tried the extendable radio shack antenna with the load in the middle and haven't been able to receive hf. Tried on a icom r-3 and was able to get a little shortwave broadcasts in english but never ham band comms. Should i most likely conclude that i will need a hf rig or dedicated shortwave reciever to pick up hf and shortwave?

Thanks
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Old 02-02-2011, 10:30 PM
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Would an indoor active antenna help me? Like the ones in universal radio: AOR Or MGJ?
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Old 02-02-2011, 10:51 PM
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I say drop some cash and get an Icom IC-R75, get that antenna outside and join us shortwave junkies in logging some serious long distance stations
YouTube - Shortwave Listening With Quality Radio

can ya put up a 45' long wire antenna? There's a nice one called the PAR endfed SWL antenna and it supposedly rocks! $80 I think.
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Old 02-02-2011, 10:55 PM
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With what you have now-just get about 15'-20' of any wire (got some spare speaker wire?) and string it along the floor in your room-then hook one end to the tip of the whip and see what you can hear it surely will be better than that whip alone.
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Old 02-03-2011, 5:19 AM
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For those that don't know, the TH-F6 is a Kenwood 2m/220/440 handheld with a wideband receiver.

HF coverage on these little handhelds is usually not very good - and it's usually due to taking various shortcuts in the design phase to keep costs down. Since we don't know where you are, it's hard to make specific recommendations, but if you're on the East Coast of North America, 6 mhz at night should be jammed with signals. 7 mhz should have lots of hams (at least up until 7200 khz or so...). In general, stay below 9 mhz at night, above this during the day. During the day, 11.6-12.1 and 15 mhz should be open.

I would also join the TH-F6A Yahoo group to see if there are any tricks to hearing HF on that little radio - user error is not all that uncommon...

An active antenna on a handheld is just asking for overload issues. Supposedly Miracle Antenna has an unamplified unit that works very well with handhelds, but it's very pricey. I would do as Ridgescan suggests and save your money for a HF rig - as you're presumably a ham, most modern ham transceivers have a general coverage rx built in. The R75 is another possibility, of course.

best regards...Mike
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Old 02-07-2011, 6:57 PM
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A radio is a radio is a radio.

There are a few internal parts - which the manufacturers has to miniaturize in order to make it all fit into one small package - but in the end, you get what you paid for.

The upside is that as long as it has a antenna jack on the radio, you can always upgrade the antenna.
The first antenna that comes to mind would be The Bruce.
http://rudys.typepad.com/ant/files/a...ray_80160m.pdf

I have used several portable scanners in the past and for FM reception a antenna of the proper length - in resonance with the frequency always works best.

For AM - a long wire antenna goes a long way towards getting good reception.
The downfall is that you will want to broadside it in the direction you wish to receive to get the best possible reception in that direction.

Most higher frequencies - the further away from the antenna you get, the more loss there is in the wire.
At 800 Mhz it might be the difference between some reception and no reception at all.

Some building materials are opaque to some radio waves - hence it is always best to mount your antenna as high as possible and away from as much ambient noise as possible - but to be careful not to have a bunch of wire left over after you install it and definitely to not have it coiled up - or it will act like a choke.

Several manufacturers makes excellent mast head pre amplifiers that you can mount close to the antenna that will compensate for the line loss in the wire.

The other half of that is that you can repurpose a old television antenna to do the same thing as long as you lay it on it's side - since most of what you want to listen to is vertically polarized.
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Old 02-07-2011, 7:37 PM
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Some good stuff here, but also be careful on some of this:

Quote:
Originally Posted by Daniel_Boone View Post
A radio is a radio is a radio.

HA HA HA! Good one. NOT!

There are a few internal parts - which the manufacturers has to miniaturize in order to make it all fit into one small package - but in the end, you get what you paid for.

100%

The upside is that as long as it has a antenna jack on the radio, you can always upgrade the antenna. Careful!
The first antenna that comes to mind would be The Bruce.
http://rudys.typepad.com/ant/files/a...ray_80160m.pdf

A Bruce Array? That's one of those antennas you see in the ARRL Antenna Handbook but never hear about in real life. Again, here's a fancy article on it, but who actually builds one? Who has the supports for one? I'd go with a Sterba Curtain or even a rhombic myself if I had the supports. I suspect that the author needed to write an article but was having a hard time coming up with a good subject, so he pulled ideas out of a hat and hence the article on the Bruce Array.

I have used several portable scanners in the past and for FM reception a antenna of the proper length - in resonance with the frequency always works best.

For AM - a long wire antenna goes a long way towards getting good reception.
The downfall is that you will want to broadside it in the direction you wish to receive to get the best possible reception in that direction.

Careful! Unless it's 1/2 wavelength or longer, it's going to be omni-directional. Even if it is 1/2 wave, if its lower than 1/4 wave from the ground, it's going to be omni-directional anyway. 1/2 wavelength in feet = 468/freq. in Mhz. For AM BC, around 1mhz ... well, do the math. As you get into the shortwaves, longer antennas (70 ft or more) have "lobes" that you can orient in desired directions. But again, the antenna needs to be up 30 feet at a minimum.

Most higher frequencies - the further away from the antenna you get, the more loss there is in the wire.
At 800 Mhz it might be the difference between some reception and no reception at all.

Some building materials are opaque to some radio waves - hence it is always best to mount your antenna as high as possible and away from as much ambient noise as possible - but to be careful not to have a bunch of wire left over after you install it and definitely to not have it coiled up - or it will act like a choke.

Several manufacturers makes excellent mast head pre amplifiers that you can mount close to the antenna that will compensate for the line loss in the wire.

Good stuff here

The other half of that is that you can repurpose a old television antenna to do the same thing as long as you lay it on it's side - since most of what you want to listen to is vertically polarized.
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Old 05-24-2013, 1:12 AM
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Would there be any compromise using a 10M 3.5mm Male Stereo Audio Extension Cable (the kind you would use for your headphones) as a "random wire" antenna to listen to a receiver such as the CommRadio CR=1? It seems like it would be easy to use. Is using something like this "shielded" so that I wouldn't not be able to hear anything?
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Old 05-24-2013, 10:56 AM
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Without getting too picky about definitions, long-wire/random wire antennas, I think you would benefit from a sort of long antenna located outside your house. Throw a wire over the roof and connect it to your radio. I would bet it will do better than the typical rubberduck. Best in the world? Nope, but it'll work. I also don't think I'd worry about 'over-load'. If it does over-load the radio, shorten the antenna a bit. If you are looking for an antenna you can walk around with, good luck, they aren't too practical.
Good luck.
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Old 05-24-2013, 5:24 PM
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I built this antenna in about an hour and with ~$25.00 in parts:

HF Receive Antenna by K0EMT

Works great on my TH-F6A and other HF appliances (AFEDRI SDR, RTLSDR Upconverter etc...). I had it thrown on the ground the other day with 20' of coax and was picking up an automated EX broadcase from New York Radio on 10051.
My biggest gripe about the F6 is trying to tune SSB. It's a bit of a headache.
but the HF RX is pretty decent for an HT.......

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Old 05-25-2013, 3:44 PM
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Quote:
Originally Posted by Kev70 View Post
..... Is using something like this "shielded" so that I wouldn't not be able to hear anything?
That is correct - it is shielded if you use it as is. To make a shielded cable like this emulate a plain old wire, you would have short the shield and center conductor together at the far end. Near the radio connector, you would have to disconnect the shield only.

The actual antenna is now the shield, using the common mode.

Obviously just using a plain old wire would be even easier to construct - but if this all you have, then you can do it this way.

About the only thing interesting about what is essentially a "reverse-fed common-mode random wire" is that you *may* observe different directionality depending upon length as compared to a plain wire of the same length.
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Old 05-25-2013, 3:54 PM
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Default Reverse fed longwire

Kev70 just gave me an idea for an antenna I've never tried before:

Using a shielded cable reverse fed by shorting the far end, and lifting the shield at the receiver is basically just an emulated bare wire itself.

Let's say we use coax instead of shielded audio cable, and instead of merely shorting the far end, we use say a 9:1 transformer at the far end connected between the shield and ground. You'd still life the shield at the receiver.

Now that would be something to play with.

Update: nevermind - I think what I'm describing here would result in a complex poorly performing terminated beverage. Maybe...

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Old 05-27-2013, 2:06 AM
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It works OK, not great. Most every handheld I've had with HF reception needed a shielded lead in due to CPU hash coming in through the antenna. To be honest, none of the half dozen handhelds I've had were really any good enough on HF to bother with. Too little wire, deaf, too much, overloading. I have a 20 foot longwire with a shielded cable connection to a BNC, and it works about as good as anything else I've tried.

A cheapo portable with SSB is light years better, and two radios are always better than one. You can buy a decent used RS DX-398 or it's clone, the Sangean ATS-909, or several others of the same type cheap on Ebay.
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