New SWL-er Here - Got Some Questions

[cc333]

Hi!

I'm new here, and am just getting started in the SW/HF listening hobby, and had a couple questions:

• I'm planning to build a 50 foot long wire antenna, but I'm not sure what I need. I've heard of baluns, and how some antenna designs use them. Do I need one for a simple long wire?
• Are long wires omnidirectional, or do I need to aim it in the direction of the signals I want to hear?

I'm planning on feeding into either a RadioShack DX-392 or DX-398, and eventually something like a DX-160.

That's it for now I think!

c

 

[ka3jjz]

Let's be a bit careful here with the terms; a 50 foot wire that is long is not a longwire but it's certainly a long wire.

Confused? It's OK because this term is very misused. A true longwire - one that is one wavelength or more at some determined frequency - is bidirectional off both ends. So if the antenna points N / S that is the way the antenna will receive best (with other factors involved). A wire that is long (and likely not that high off the ground) will basically be omnidirectional (again, with other factors such as frequency being operated involved here, along with ground conductivity and other factors)

A balun - a device that takes a balanced feed like a single wire and uses an unbalanced feed (like coax - hence its name) would likely not buy you very much, but it certainly isn't going to hurt anything. Those old radios would probably work OK with it as they're pretty tolerant of this.

You don't say where you are, but that might be about as long as you want to make it if you live near an area with lots of MW, FM or TV stations nearby. Those radios aren't hard to overload; this shows up as stations on frequencies where they don't belong. There are ways to mitigate this, though.

Mike

 

[jwt873]

Welcome to Radio Reference...

When I was a teen living in my parents house, I had a 50 - 60 foot wire run from a second floor bedroom to a clothes line pole at the back of the yard. It worked great for what it was. I managed to copy all sorts of SW stations using an old tube type DeForest Crosley short wave set.

50 feet of wre won't perform that well when you get under about 4 MHz. You'll still hear things though.

Generally antennas are directional off the broad side.

They say a 9:1 balun is supposed to help.. I actually don't know, I've never used one but I agree with ka3jjz.. I doubt you'd gain that much on receive. I'd imagine that they are more important if you're transmitting where a match is much more critical,

I would have loved a DX-160 back in my day. I used to drool over radios like that when i was paging through Rad Shack catalogs

 

[Boombox]

50 feet will be fine. You don't need a balun. Baluns are for the higher performance situations. For most of us, simple wire antennas for SW -- whether indoor, or outdoor, work fine.

The main issues are RFI (interference from computer equipment, switching power supplies, etc.) which you can get from nearby houses (including your own) and static electricity discharges (which can zap a radio), which can come from nearby T-storms and dry, winter wind. Never leave an outdoor antenna attached to your radio during winter storms (dry air can cause static discharges) or thunderstorm activity.

I would avoid attaching an external wire to your DX-392. Those radios don't have static discharge protection. A static discharge (not talking a lightning hit -- that will fry anything -- talking a static electricity discharge off the antenna into the radio) can fry the DX-392's RF amp transistor. You'd be better to try a shorter, indoor wire for that radio.

Your DX-398 will work fine with an external wire, though. It has internal diode protection against static.

Still, outdoor antennas, winter and T-storms do NOT mix.

The best thing to do would be to try a shorter wire and see how it works with your radio. Try an indoor one and see if that boosts signals enough. I use an indoor wire and do OK. I don't have a lot of RFI in my home, which helps. My indoor wire is around 30 ft.

RE: directionality: wire antennas only become particularly directional when they are over a wavelength long. A 50 ft. wire will probably be omnidirectional at the SW frequencies, or partly bi-directional higher up the SW band. I wouldn't worry about directionality at first. Experiment with your antenna and keep your radio safe from static discharges.

Last but not least, if you actually erect an external 50 foot wire, make sure it has some sort of lightning protection, and a way to ground the antenna when not in use.

Good luck. It's a fun hobby -- when the ionosphere is participating.

 

[popnokick]

For DIY construction (or to purchase) you may want to look at this antenna and its receiving radiation patterns -
EF-SWL Antenna | PAR Electronics | Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave listening enthusiasts
... and read the reviews on eHam that include info on random wire antennas -
https://www.eham.net/reviews/view-product?id=3707

 

[ka3jjz]

You really can't go wrong with the PARs. You can change out the antenna element if you like. The connection box takes a bit of tinkering to see what setup works best for you, but that's part of the fun...

And as for static suppression - this thread goes into this in some detail. You can build the box for this if you can find the parts and know how to solder. It's a great first timer project, and it can be used on any radio, not just portables...

Static drain for outside long wire antenna

Up until now I've used the old tube radios I collect and restore for DXing. I use a 50' outside wire for my antenna. Static (other than lightning) isn't a problem for tube radios. But I decided I wanted to try one of the new portable radios and ordered a Tecsun PL-880, which should arrive in a...

forums.radioreference.com

Mike

 

[cc333]

Wow, that PAR antenna looks like it might be just what I want! And at ~$75, it's within reason for me to save up for.

In the meantime, though, I'm still going to set up a plain old random wire antenna as an experiment, if only because it's free (I already have a spool with at least 100' of 18ga magnet wire still on it that I can use).

I'll have to figure out some static protection for the DX392, so I might try the DX440 instead. However, it seems somewhat less sensitive than the 392 for some reason (I've read that the DX440 is supposed to be quite sensitive). I'm guessing that this means it needs to be realigned and recalibrated. With a decent enough antenna, it should still work pretty well nevertheless.

I also have one of those Radio Shack amplified SW antennas, which has an external antenna input. Can it be used as a means of protecting the radio?

c

 

[Boombox]

If you build the project that KA3JJZ linked, your DX-392 will be safe.

Another thing you can do -- if you're handy with soldering, is solder two back-to-back diodes between the antenna soldering pad and the negative battery terminal, inside the back of the radio. You can do it with two diodes and hookup wire. I did this to my DX-390 (a DX-392 without the cassette player) and have had no negative effects. The diodes will bleed off stray static charges, and even protect the radio should you walk across a carpet in dry humidity and touch the whip (which could zap the radio).

It entails removing the back, finding the antenna's connection to the PCB, and wiring to back-to-back (reversed) diodes to the negative battery terminal using hookup wire. I used tape around the diodes and any parts of the wire that had exposed metal, in the case they'd somehow touch against the PCB. I still use the DX-390 20 years later.

RE: The DX-440: you would want to have external static protection with that radio, too. Sangean did not include internal diode protection in their radios until they made the DX-398 (Sangean 909), although the mid- to late-1990s Sangean-made DX-375 has them included.

A simple rigging of two reversed diodes and/or a large resistor (I've seen one megaohm suggested) will protect it if you attach them between the external antenna and a ground.

Similar to this simple project, from another RR thread.:
Static drain for outside long wire antenna | RadioReference.com Forums

You could leave out the potentiometer and still protect the radio.

Indoor antennas are probably safe, though.

Another 'solution' is to 'connect' the external antenna inductively. Wrap the lead around a tube (paper towel of toilet paper tube will do), and set it near the radio, without making a direct connection. Sometimes that works. It might work better if you had the non-antenna side of the coil connected to a ground. The RF field can often increase reception to the radio, although YMMV.

 

[swlqsl]

Another Great Wideband Antenna & Not Expensive By Tecsun
Tecsun Discone Antenna

 

[prcguy]

If your receiver has a screw type terminal for a wire you can connect 50ft of wire to that screw and it should work ok. That type of input is generally a high impedance input and designed for random wires of varying impedance at different frequencies. If the radio has a 50 ohm connector like an SO-239 then its better to use something like a 9:1 balun with coax between the receiver and balun then the single 50ft wire off the balun 600 ohm tap.

A 9:1 balun will help smooth out the match to a random length of wire used across a wide range of HF frequencies and it will also help a little in keeping some RFI from riding up the coax from your radio room computers, etc, to the antenna where it can get picked up by the receiver. I would recommend keeping the antenna far away from the house and feeding it with coax to keep down interference from noise generators in the house and I would also use a good common mode RF choke in the coax line in addition to a 9:1 balun or transformer.

 

[KB2GOM]

I live in an antenna-challenged situation and got some decent results with this:

Jock designs a Horizontal Room Loop to cope with reception issues

Many thanks to SWLing Post contributor, Jock Elliott, who shares the following guest post: Got reception issues? An idea worth considering: the “Horizontal Room Loop.” by Jock Elliott (KB2GOM) When…

swling.com

In addition to the very helpful folks here at radio reference,you will also find some helpful folks here: SWLing Post Message Board - Index page

One thing is for sure: do not EVER put up your antenna where it can fall on a power line or a power line can fall on it.

 

[dlwtrunked]

Another Great Wideband Antenna & Not Expensive By Tecsun
View attachment 132702 Tecsun Discone Antenna

He is talking HF/SWL and hat is a terrible antenna for such (even the maker gives the end as 25 MHz).

 

[N9JCQ]

Another Great Wideband Antenna & Not Expensive By Tecsun
View attachment 132702 Tecsun Discone Antenna

The Discone is for VHF/UHF frequencies. It may "receive" HF frequencies but it is tot optimized for it.

 

[p1879]

I once had the DX 440 and the Radio Shack SW antenna amplifier. With a 30 ft. wire on it, and using the tuning control to peak signal, it does pretty well for Shortwave.

When I was fascinated with HFDL, and ALE signals, and SW broadcast listening I used a Par Endfed antenna with an Icom R71 and later a R75. This is a seriously good dx antenna. Getting it up high had a big effect on HFDL aircraft plots; when the antenna slithered out of the tree in a storm, and was hung lower, the signals from Africa and far Pacific disappeared. This antenna is still around and made by LNR Precision, to my understanding.

 

[popnokick]

I put a link to the Par EF-SWL earlier in this thread of msgs.

 

[cc333]

I just put 50-ish feet of wire up on the roof (not ideal, but it's the highest place I can find that doesn't involve climbing trees), and the results are, well, disappointing so far.

It feels like I'm picking up more noise than anything, although it does seem to overcome the RFI from my computer, which is strong enough that any radio with a whip or ferrite core loop antenna simply doesn't work for AM or SW.

I'm using a Radioshack DX-398/Sangean ATS-909 and Radioshack amplified SW antenna (though reception seems slightly better without it, which is to say slightly less noisy). Would a balun help any? At the very least, it would probably simplify the feedline and ground situation, which is made up of scraps right now (this could be partially why it's not working as well as expected).

Or would a loop be better? This one, for example?

And, for loops, I don't have to rotate it to receive all signals, do I? My understanding is that they're relatively omnidirectional, and the main purpose of rotating is to point the null at an interference source (a fluorescent light fixture or switching power supply, say) to cancel it out, yes?

c

 

[Boombox]

Wire loops are omnidirectional if they're horizontal, like many people erect (a large loop around their back yard, for example). If they're vertical, then they're like a quad, which can be directional. I have no idea how the modern loops that are manufactured operate -- I think they're directional, which might be a reason the SWLs get them, they can rotate them to null out noise.

Your DX-398 will handle an external antenna well without overloading, so any outdoor antenna will work with it OK, performance-wise.

 

[cc333]

Can the kind of wire have an effect?

I had a revelation the other day that the wire I used might be part of the problem, so I found some super lousy TV cable from a cheap amplified antenna, which happens to be close to 50 feet, and draped it over the garage roof for testing. I can't tell quite yet, but I think it's a bit more sensitive.

Either that or propagation is more favorable.

In any rate, I'll probably use the cable, since it's probably more appropriate for outdoor use anyway, at least more than the speaker wire I used.

I also have more of it (also close to 50 feet long) that I can do one of two things with:

1. I can string them together for a 100' line, or
2. I can connect both of them to the feedline and have a dipole arrangement.

Which would be better?

I also plan to get an active loop at some point, but if I put it on the roof (which I believe is ideal), I'd have to also get an antenna rotator setup so I don't have to climb up to re aim it every time I change frequencies.

c

 

[ka3jjz]

Loops work just fine closer to the ground (some references say no more than 6-8 foot, others no more than 1 loop diameter) in order to take advantage of propagation on MW and LW that tends to be lower to the ground. It allows the loop to discriminate directions. On HF above 2-3 Mhz that ability is pretty much lost as skywave propagation starts to predominate.

So no climbing on the roof needed....Mike

 

[cc333]

That's good to know, thank you!

Since I don't need to put it on the roof (which saves me the expense of getting an antenna rotator), maybe instead I can put it on a tripod or some other sort of stand, so it can be more easily and precisely moved.

Also, while we're on the topic of loops, would a loop 9 or so feet in diameter be any good at transmitting ~100 mW at 1610 kHz? I suspect not, but I thought I'd ask nevertheless.

c