Longwire Shortwave Antenna Help

[N1BHH]

It's overkill putting a 100 foot wire into any of those Grundig or Sangean radios. It only needs a relatively short wire as the radio will overload on strong signals. You may be asking for trouble by hooking up a big wire. I used the rain gutters in one of my previous residences and that worked fine, just hooked up a wire long enough to reach the radio and it worked well on my old DX-440. I have a Grundig Yachtboy and if I put my extended double zepp into it, it gets trashed from signals all up and down the bands. Most other portables do the same thing. Filtering in communications receivers is much better than a portable type radio.

 

[nanZor]

Portables with large external antennas are overkill and usually suffer overload, negating all the hard work. Been there with my G5 and others.

The fastest, easiest way to improve performance to a portable is to add the missing component - an RF ground. For an RF ground, no waterpipe connection needed. Just throw about 10 feet or more of wire on the carpet, or tack it neatly to the baseboards, and find some way to attach to the ground on the portable. You might even have to use just a pressure fit for the radio ground with some tape. Be sure you are running on BATTERIES for safety reasons.

You can use your existing whip as the main antenna, or if you have an external antenna jack, so much the better as you can attach the floating RF ground wire there and also perhaps 6 - 12 feet of wire for the center-conductor antenna connection. (Purists would want a 1/4 wave of wire for the rf ground for each band of interest, but for a portable just 10 feet for an rf-ground should be reasonable all-rounder)

Again, with portables, I only do this while running on batteries since I don't trust the overall safety of portables and floating grounds while connected to cheap ac wall warts.

So a simple "throw down" rf-ground wire, would make a world of difference.

Re the metal-roofing: A few years ago I had this done and thought that my indoor antenna days were over. Not so! Provided that your walls aren't totally shielded, and if you have some large windows, believe it or not, an INDOOR VERTICAL can work pretty well. Obviously not as well as outside, but with the vertical's low-angle of radiation, I only got attenuation from high-angle daytime short-skip contacts - otherwise, plenty of dx was heard for the incoming low-angle skip.

Noisy vertical? You bet! However, with the portable, I was able to walk around the house, and scout out a very thin "slice" where the vertical wasn't susceptible to any noise in the house. (This scouting trip was for a more robust tabletop receiver) It took awhile to find it, and I only had about a 3-foot area to work with before hearing all the junk - so I made that area the place for the vertical. Here again, the key was to get a good RF ground, and that entailed running 1/4 wave floating ground wires (234 / f Mhz) from the antenna ground down along the baseboards for the bands I was interested in. Alternatively, I also used a few 1/4 wave ground wires straight from the ground screw of the Icom R75 and the ends just tacked in place on baseboards or hidden under carpet. (RX ONLY)

Obviously I wish I could have put this vertical outside, but the low-angle loaded vertical whip inside didn't really "see" the metal roof above it, and performed as well as it could when that "noiseless" indoor location was found. The key to keep the radiation angle low was to get a good rf-ground.

Food for thought anyway for portables and / or metal roof construction...

 

[xmusicianguy]

(sorry to bring back a year old thread)

I too have wired up a Longwire SW antenna. I read up on a website that it would work. I went to Radio Shack and bought a 100 FT 18 gauge insulated (speaker) (NOT SHIELDED) wire. I then strung it up from my room the radio is in to several trees. High as I could get it. I then ran it to a RG-6 line to the center pin and ran a dedicated ground rod that is a common for satellite TV and cable hookups to the outer braiding. I have issues with the ground however. I had a much smaller setup before running about 5 FT outdoors also. I had that grounded too but got ZERO resistance. Issue with this ground is I'm getting alot of impedance or resistance in the line. I took my multi-meter to it and got around 56.0 to 60.0 Ohms on the ground side. Even some DC mV are coming through (about 8.0) It's a straight run. I didn't have the issue before. I tried using hq cat-5 cable and what I had left from the speaker wire. I even soldered the connections. Still no luck. I wanted to ground as I figured a true earth ground would improve signals vs a floating ground. Plus I wanted to wire up a bridge between the antenna wire and ground for lightning arresting.

Now what is my issue. Is what many others and the OP said. I'm having RF overload. I have a Grundig G3 and a Tecsun PL-230. Both have a EXT antenna jack that is 1/8" jack. (mono?)

Like many have said in this thread I'm getting a lot of AM stations in frequencies all over the spectrum. It's making it so even N America aimed SW transmissions are kicked off due to the overload. 5000kHz (WWVB) is barely receivable (I'm in TN the station is in CO). I spent a small bit of money to get a setup that would pull in weak stations and filter out all of the EMI in my room from TVs, Computers and such. I've HAVE found I can use RF inducing to get the signals to the radio. Getting the RG-6 cable close or touching the antenna on the radio seems to work ok. However I have no way to keep it there. I've read all the comments in this thread. But am confused. Is there a cheap RF filter I can obtain. Or even put a resistor inline with the antenna feed (not the ground line). To reduce some of the signals in the line. Even a Low-Pass RF filter to block the AM stations from taking over. Know that would reduce the performance some. But right now my setup is almost useless.

I've "drawn" a stick image of my setup. Wire inside is RG6 to a phono 1/8" connector. GND is listed too. Line is over 100 FT. Straight run. Yellow square is a line hold block.

Ideas? Thanks!!

 

[ka3jjz]

No - and here's the reason why. Both of those portables are not designed to handle the amount of RF that a 100 foot wire (and I'm deliberately not calling it a longwire - that is a completely different animal - although you can say that it is a long wire). As you suspected, you are overloading both radios very heavily. A desktop (say a R-75) is designed to handle such loads easily - those 2 portables won't.

I'm not so big on hooking up a ground to the same one used by a satellite system and cable hookups. There's no way to validate that the ground was done properly. RF grounding is a whole lot more than just ramming a ground rod into the ground - there have been MANY discussions about this very topic in the past, and whole sections of books devoted to this.

Trying to shield out RF from computers and such with radios with basically plastic cases is next to impossible, really. The antenna isn't the only culprit here - the RF can go right through that case as if it really isn't there. There's the additional possibility of having it coupled through the wall wart - which is notorious for poor shielding in the first place. You need to stop it at the source - and again, there have been whole books written on this subject.

Let's start with the antenna. Both portables probably couldn't handle more than 20-30 foot tops - perhaps a bit more but not by much. I wouldn't at all be surprised if even this amount is a bit too much at times. If it were me, I'd stick to the small amplified loops - which have the advantage of being able to move them around to find a quiet spot in the room. The Kaito KA33 is one example.

Now if you have some soldering and constructing skills, the Carpet Loop antenna I used to use a while back - and it was quite interesting. I had it on a TenTec RX320, and found it worked pretty well. The wire element can be as big (or small) as you like. The links for both, and much more, can be found here...

Loops - The RadioReference Wiki

The best lightning arrestor is disconnecting the radios from the antenna (and if you can, ground the feed line) during a thunderstorm. Arrestors aren't a panacea - they can and do drain static charges, but they can and do fail. Too, they're generally set up for coax feedlines - and most small portables like you have won't perform very well with low impedance inputs.

best regards...Mike

 

[xmusicianguy]

No - and here's the reason why. Both of those portables are not designed to handle the amount of RF that a 100 foot wire (and I'm deliberately not calling it a longwire - that is a completely different animal - although you can say that it is a long wire). As you suspected, you are overloading both radios very heavily. A desktop (say a R-75) is designed to handle such loads easily - those 2 portables won't.

So I need first off is to cut the wire back to about 30 FT MAX.

I'm not so big on hooking up a ground to the same one used by a satellite system and cable hookups. There's no way to validate that the ground was done properly. RF grounding is a whole lot more than just ramming a ground rod into the ground - there have been MANY discussions about this very topic in the past, and whole sections of books devoted to this.

The ground I'm using is the ground for my home electrical meter. So it should be a proper earth ground

Trying to shield out RF from computers and such with radios with basically plastic cases is next to impossible, really. The antenna isn't the only culprit here - the RF can go right through that case as if it really isn't there. There's the additional possibility of having it coupled through the wall wart - which is notorious for poor shielding in the first place. You need to stop it at the source - and again, there have been whole books written on this subject.

I'm so freaking stupid on that front. You are so right. The EMI is going right through the radio case making it 10 Xs worse

Let's start with the antenna. Both portables probably couldn't handle more than 20-30 foot tops - perhaps a bit more but not by much. I wouldn't at all be surprised if even this amount is a bit too much at times. If it were me, I'd stick to the small amplified loops - which have the advantage of being able to move them around to find a quiet spot in the room. The Kaito KA33 is one example.

I'd go that route. BUT I have a large brick wall that the room is attached to (room was a add on) that blocks alot of signals. Hince the second need to a outdoor antenna.

Now if you have some soldering and constructing skills, the Carpet Loop antenna I used to use a while back - and it was quite interesting. I had it on a TenTec RX320, and found it worked pretty well. The wire element can be as big (or small) as you like. The links for both, and much more, can be found here...

Loops - The RadioReference Wiki

I have some construction and soldering skills. I soldered the "wire" antenna I have now. I've also tried overhead runs before. More like a dipole type. But in a L fashion. This was a total train-wreck. My desktop computer, TV, etc caused more noise in the radio than ever. A carpet loop probably would be worse as it would be closer to the source.

The best lightning arrestor is disconnecting the radios from the antenna (and if you can, ground the feed line) during a thunderstorm. Arrestors aren't a panacea - they can and do drain static charges, but they can and do fail. Too, they're generally set up for coax feedlines - and most small portables like you have won't perform very well with low impedance inputs.

My plan for lightning arresting was a coax coupling disconnect from the radio. Also solder a piece of RG-6 from the copper center pin to the outer braid connection that was grounded.

best regards...Mike

Thanks for your info. I also had considered taking down the speaker wire and stringing RG-6 about 30-40 FT then going to the radio. I saw a video of a guy in Australia used a 20 FT RG-6 line and ran (ungrounded) the center pin straight to the radio with no interferrance. Maybe because it was shielded then it rejected more powerful signals. But if I know my electronics knowledge (may not) well then if it is shielding the high power stations the low power stations or weaker ones stand no chance.

What ever route I need to take I want to take it. I also want to pickup the 40M amateur radio broadcasts without interference. I guess I do have on my side that the Computer and TV equipment is on one side of the room and the SW Radio is on the other. That should help.

I still wish I knew what the impenitence rating was on these portables. I'd like to match it.

Anyway. Thanks man. I see you are a Amateur Radio operator. I too am looking to get a Technician class license. That's another story though.

 

[a29zuk]

Let's start with the antenna. Both portables probably couldn't handle more than 20-30 foot tops - perhaps a bit more but not by much. I wouldn't at all be surprised if even this amount is a bit too much at times. If it were me, I'd stick to the small amplified loops - which have the advantage of being able to move them around to find a quiet spot in the room. The Kaito KA33 is one example.

best regards...Mike

Yes, before I purchased my Palstar, I used the Grundig YB400 portable. I experimented with different random wire antennas but I got the best performance just using a 6' copper tube mounted to my light tower(insulated from the tower,of course) about 30' above the ground. The height of the antenna especially improved the signals on the lower frequencies(2Mhz to 5Mhz) without any overload from the broadcast band. The random wire antennas were too long and overloaded the receiver even when they were only 15' long. But as Mike stated above a loop is also a good alternative.

Jim

 

[xmusicianguy]

Would reducing my overall wire run from 100FT to 30FT help any? Or do you all think I'd overload the radio again. I tried a 6FT antenna run prior. It was only about 10 FT off the ground however. I even considered making a dipole and using a 300 Ohms to 75 Ohms transformer to the radio. I'd still like to solder a ground mainly to rid the line of static discharge and EMI in the line.

 

[ka3jjz]

I suspect it would. And I would ditch the 300-75 ohm transformer idea. It's quite likely both radios are set up for high impedance inputs - probably on the order of 500 ohms or even more.

The ground that is used by an electric meter is likely not a RF ground - it's an electrical ground. Never assume the 2 are the same - they aren't. I'm sure someone here can come up with a good brief explanation - I'm drawing a blank at the moment....

Oh by the way WWVB is a longwave station - WWV is the HF station, both out of the Colorado area.

WWVB - Wikipedia, the free encyclopedia

best regards...Mike

 

[xmusicianguy]

I suspect it would. And I would ditch the 300-75 ohm transformer idea. It's quite likely both radios are set up for high impedance inputs - probably on the order of 500 ohms or even more.

The ground that is used by an electric meter is likely not a RF ground - it's an electrical ground. Never assume the 2 are the same - they aren't. I'm sure someone here can come up with a good brief explanation - I'm drawing a blank at the moment....

Oh by the way WWVB is a longwave station - WWV is the HF station, both out of the Colorado area.

WWVB - Wikipedia, the free encyclopedia

best regards...Mike

I know that the ground used by the electrical meter was a electric ground not dedicated RF. I just figured any earth ground would work. I'm still a beginner as sorts into electronics. I understand how alot of it works. But somethings still elude me. I still need a way to ground my setup for both electrical reasons such as a surge or lightning and static buildup. But also as a earth ground for the RF signal to pass through.

Also I realized that I labeled the WWV station wrong. Forgot to change it however. As far as the antenna. I just want to do this right and safe and effective. That is why I don't want to use a floating ground OUTDOORS for the antenna. Unless I can electrically ground it for safety. But then I guess I can do both? Floating ground for the RF and earth ground for the electrical and static buildup. Build a Dipole antenna?? Thanks

 

[a29zuk]

I know that the ground used by the electrical meter was a electric ground not dedicated RF. I just figured any earth ground would work. I'm still a beginner as sorts into electronics. I understand how alot of it works. But somethings still elude me. I still need a way to ground my setup for both electrical reasons such as a surge or lightning and static buildup. But also as a earth ground for the RF signal to pass through.

Also I realized that I labeled the WWV station wrong. Forgot to change it however. As far as the antenna. I just want to do this right and safe and effective. That is why I don't want to use a floating ground OUTDOORS for the antenna. Unless I can electrically ground it for safety. But then I guess I can do both? Floating ground for the RF and earth ground for the electrical and static buildup. Build a Dipole antenna?? Thanks

Basically your receiver is already eletrically grounded through your wall wart power supply that you have plugged into the wall outlet. When you are running a ground wire to your electrical meter(especially when it is a long way away) it is acting part of an antenna system and picking up a lot of man made noise from various appliances in your home. Grounding your receiver near your antenna is the best bet for reducing noise especially when running it on battery power. This sort of RF grounding is part of your antenna system.

I've gotten into the habit of unpluging my antenna from my receiver whenever I'm finished using it for the day.

Jim

 

[KC4RAF]

As mentioned, RF ground and electrical grounds

are different. The RF ground should be as short as physically possible, otherwise as note previously, it becomes an interference pickup. Sorry to repeat all the other posts, but just stressing the importances of RF grounding with you all.