Antenna tuner

[LarryMax]

Not sure why I was so oblivious to this but, Anyone who monitors HF (NON TRANSMIT). Should really look into getting an antenna tuner.

For some reason I never thought having a tuner would do anything for receive. Big mistake on my part. I never really thought about it and it just didn't make sense to me to have one for receive only.

I just keep pondering the the hell I've been through the last few years. I'm glad the light bulb finally came on in my head.

Geeez!!

[ka3jjz]

Well, there are purists out there that say that if you're hearing signals, then enough signal is reaching the front end of the receiver, and a tuner won't add anything to the equation. However, for folks (like myself) who have to work with other things to 'create' an antenna out of an existing structure (say, trying to use an air vent as an antenna), a tuner is going to help make sure that as much signal as possible reaches the radio. Some of the better ones have a bypass position so you can compare the difference (the old Grove TUN-2 had this, for example). The same could be said for any indoor antenna, or one that is less than optimum...

Unfortunately variable caps are much harder to come by these days, although I understand there are still a few places that have them (in fact, I thought I saw something in a recent MFJ catalog on this). There are still some schematics floating around out there - in fact I remember way back when I built a little pi-network tuner for an older radio (a Hallicrafters SX110 which I restored from a near-lightning strike) that worked quite well.

73 Mike

[nickcarr]

I recently bought a MFJ-959C to try out. I was curious if it would "improve" my current set up. It's basically a matching transformer with a built-in preamp.

Without the preamp turned on, I couldn't tell any real-world difference (i.e. my ears didn't detect anything different.)

I hooked up my MFJ-259B to analyze the results and there were times where I improved resonance by a small amount.

Overall, I chose to sell it as it really didn't seem to help an already "good" set up. I should have spent more time testing the 959C but I didn't. I feel it would be great for someone (as Mike suggested) who needs help in finding a perfect match with a non-standard antenna.

The one lesson I learned was that the numbers don't always translate into what you can distinguish via the ear. (i.e. Even a bad antenna can bring in good results.)

[LarryMax]

Yes, I am using rain gutters. House is 3 years old so they are pretty new. They are also countinous around my house. My rough measurements put it at about 150ft of antenna. I can't believe how much better the tuner has made my reception.

[nickcarr]

So are you using coax directly on the gutter or do you have some other setup? I'm curious how your bringing the signal to your radio?

It should work well but the only downside is that it's close to the house-noise.

[LarryMax]

Yes, the coax is currently connected straight to a downspout (center conductor only). This was a quick let me see what happens install. And yes, Noise is an issue. I am currently pondering what to do with the shield of the coax. What I really want to do is cut out a small section of the gutters (up on top of the house) and replace with a plastic piece of gutter. Then do the right thing and attach the center conductor to one side and shield to the other.

Of course other possibilities are run shield to house power ground (a pretty big job) or run radials in the ground with the shield.

As for now, I am content. I finally moved out of the Orting Valley (RF hell hole) and bought a house up on a 1000ft hill behind Orting. So my chances of reception improved greatly. Adding the tuner was the real kicker. All I can say is that it worked and worked well.

The next step is buying a real HF rig. What I'm using now is a complete joke.

[nickcarr]

Hmm, I would try running the coax center to the lowest point of the gutter. (So near the ground.) Then I would take the coax shield and attach that to a new ground rod. That should help with some of the noise.

No room for a wire antenna? ...or the Mrs won't let you?

[LarryMax]

Hoa

[ka3jjz]

Larry, you might consider adding a 9:1 transformer (i.e. a magnetic longwire balun) to your setup. To keep things on the cheap, the SWL antennas yahoo group has both plans and fairly technical discussions on the subject. You might then find that you may not even need the tuner any more.

As a test, if the tuner has a 4:1 balun (many MFJs do), then I'd try using that first. In addition that Yahoo group has some neat antenna ideas that you might be able to hide - even running a wire along the fence, around the perimeter of the yard, and feeding that with a 9:1 balun might be worth trying.

Both might help your noise issues and bring your reception up a bit more. These days with crappy propagation, every little bit may be helpful

73 Mike

[edit] Another possibility is something that I had in my attic, but there's no reason why it couldn't go outdoors - string a loop around the perimeter of your roof (use clear insulated wire, nice and thin), bring that down to a 9:1 transformer and have at it. Loops can reject certain kinds of noise, depending on your environment, and they're very good for DX as well. I actually built the carpet loop (the plans are linked in our wiki) because I can't be Spider Man hanging around my roof, hi

[ab3a]

Larry, I'm not sure what the scale of your whole antenna system is, but something tells me that if you're noticing a distinct difference when using a tuner to match your "antenna" system, then it may be a lot shorter electrically than you think it is. If you really had a continuous gutter antenna running for 150 feet, you should have had plenty of signal to begin with. In other words, I'm suggesting that perhaps your rain gutter antenna idea isn't working, and you're only picking up signals from your feed line.

If you have an HOA, you might try some of the following ideas: If your gutters are white, use white wire and run it around the outside of your gutters. Be neat about it, so that nobody notices what it is.

Alternatively, try laying the wire in the gutter and then run the coax down the downspout.

Another favorite scheme for receiving antennas is to use very thin magnet wire and run it out to a tree. Unless you're only a few inches away, you'll never notice it. The disadvantage is that neither will the birds. They tend to run in to it and break the wire.

Yet another scheme that works is to disguise the antenna as a flagpole. I've seen that done with such stealth that no-one could tell what it really was.

In the long run, however, if the antenna is close to the house, you'll probably want to isolate it from your radio and electric system. That's where the RF isolation transformer comes in. Build the antenna first, and then, if you hear lots of static or interference from computers, light dimmers and the like, then I recommend isolating the whole thing with an unbalanced to unbalanced transformer.

Last, but not least, don't overlook some of the small active antenna kits. A short antenna with a high dynamic range amplifier can be impressive on lower bands. But do be careful because there are lots of pretenders out there.

[LarryMax]

I appreciate the advice. And I thought about the gutters not being "linked" together very well. I am lucky enough to have equipment to tell me those things. I'm a sweep tech for the big bad cable company and I have access to ridiculously expensive RF measurement equipment. Since I work with a "closed" system things are a bit perplexing to me when it comes to "open air" communications. Closed systems are all I know. Thankfully my SDA 5000 (look it up on google I have the 9000.00 dollar version) has quite a few things I can use for antenna tuning and TDR'ing. According to my meter my electrical length is 147ft. Even if my feedline is included it's only about 20 ft.

I'm still trying to figure this whole OTA thing out and then try and go to work and do my job properly. It seems things bleed over into both aspects.

[gcgrotz]

I used to have a good friend in Columbia MD (BIG! hoa) that used his gutters on 75 meter ham band. He was pretty weak most of the time but it worked. You should use a ground rod or more for the shield at the bottom.

As for a tuner, I find that even with the good rx in the Icom 746pro, I get bad overload from a 1kw AM nearby. When I switch on the internal tuner, most of it goes away. Same for the external tuner I use sometimes. The MFJ-956 works good ahead of the Icom R75 as a preselector, again, keeping out the local AM station.

[nickcarr]

I had to buy the ICE BCB filter for my SWL set up. The AM stations would just kill any attempt to listen below 1800khz. It works very well - and I can actually hear HAMs on 160m.

[LarryMax]

I moved the radio room out of the garage and moved it to its permanent location upstairs. I removed the gutter setup and ran 70ft of #14 ground wire in the attic. Works better for some things, worse for others. Could be conditions though, I'll need more time to tell.

[raisindot]

Originally Posted by ab3a

In the long run, however, if the antenna is close to the house, you'll probably want to isolate it from your radio and electric system. That's where the RF isolation transformer comes in. Build the antenna first, and then, if you hear lots of static or interference from computers, light dimmers and the like, then I recommend isolating the whole thing with an unbalanced to unbalanced transformer.

Sorry to but in here, but can you explain the "unbalanced to unbalanced transfomer" concept in terms that dummies like me can understand? I've got a PAR EF-SWL matchbox thing with around 120 feet of long wire running in a semi-slope from the basement windows to the trees. It's fed through a standard coax cable to my JRC 545. I've got both the antenna and the coax shield (which are groundable through posts on the PAR matcbox) grounded to the ground rod next to the house.

Even with this configuration, I still get a huge amount of buzzing noise, particularly on the lower end of the spectrum. Strong stations do come in very well, however.

Before winter comes, I'm going to try using longer coax underground and moving the EF SWL matchbox about 40 feet from the house. But the transfomer idea also sounds interesting. Is it different than a standard bailun concept or what I have already, and is it relatively easy for a moron like me to set up?

Suzie

[ab3a]

People have literally written books on the subject of RF transformers. However, here is a cheap overview:

Basically, a balanced antenna presents symmetric load to each terminal of the radio. A balanced transmission line does the same. Ladder line or H-line is balanced. A dipole is balanced. A loop is balanced. An off-center fed random wire is not.

Likewise, a coaxial cable is unbalanced.

From an SWL's perspective, this isn't much of an issue --unless your house is a source of a great deal of electrical noise. If it is, you'll want to minimize that noise. Moving the antenna away from your house is one measure you can take. But still you may hear some noise. The problem is that your coaxial cable may be acting as part of the antenna system instead of just bringing the signal to your radio. As the coax gets closer to the house, it can pick up more and more of the very energy you're trying to get rid of.

What you can do instead is to feed it to an Unbalanced to Unbalanced broadband RF transformer. This effectively isolates the transmission line from the antenna, and keeps it from becoming part of the antenna.

Look up UnUn RF on your favorite search engine and you should see plenty of information on what these are and how much they cost.

[nickcarr]

Originally Posted by raisindot

Even with this configuration, I still get a huge amount of buzzing noise, particularly on the lower end of the spectrum. Strong stations do come in very well, however.

PAR gives you a 9:1 transformer already - that's what that box is that you plugged the coax in to.

Without getting all technical, the 9:1 ratio is needed because they're trying to give you a "broadband" (or wide-range) of frequency usage. Also, one really important factor in wire antennas, is to get them as high as possible. For example, a wire antenna at say 50ft (from the ground) will be much "quieter" than the one at 6ft. So in general, the higher you can string up that antenna lead, the better the results.

Moving the antenna out, away from the house will be one positive step in reducing your noise.

The buzzing you're hearing is likely from your house AC. Ideally, you need to ground the radio (to a ground rod outside the house) and then at the antenna end - have another ground rod which connects to the transformer box.

For some extreme cases, it may be necessary to buy an AC filter for your radio.

Filters RF | Telephone

Here's a review of it in QST magazine: http://www.iceradioproducts.com/imag...ersarticle.pdf

Also, this email is very good article and easy-to-understand explanation of what's going on with your "noise" problems:

Grounding is key to good reception, was: Experience w/NRD-535 - rec.radio.shortwave | Google Groups