Monthly Archives: December 2015

Laser-engraved box cover–you like?

Enraved CoverI found a great deal on a small laser engraving machine and decided to try engraving the cover of the matchbox instead of affixing a paper label. The paper label can make the box more visible in some cases and this isn’t good when stealth is the goal. Besides, the label really isn’t essential; I doubt you will forget the box’s purpose, especially once it’s deployed.

Still, some may prefer the paper label, so I will continue to enclose one if you want to attach it over the engraving. My question is: Do you like it, or should I stick with the paper label?

Hit replay, or use the contact form to let me know what you think.

73,

de W4KGH

Using the W4KGH SWL receiving antenna

The W4KGH SWL antenna does not require any assembly; it is ready to deploy.

Your site layout–or your personal preferences–will dictate how to hang the antenna. Hanging the antenna horizontally will take up the most real estate and is usually not feasible in an urban setting or a small subdivision lot. A vertical installation can work if you have tall trees on your lot or live in a high rise apartment or condominium (drop it from a sixth story window, for example).  An inverted vee or sloper configuration is usually practical just about anywhere. The idea is to get the end of the antenna or the apex of the vee as high as you can.

My personal preference is the sloper. This configuration has an omni-directional receive pattern closest to that of a vertical antenna, especially at lower to mid HF frequencies. It also allows you to keep your ground run short and close to the end of the antenna.

How you configure your ground will depend on conditions at your location. The antenna matchbox contains a 9:1 impedance matching transformer with both the primary and secondary grounds connected to separate studs on the matchbox (B & C in the photo). Normally, you would want to short these two connections and connect them to ground. You could also leave this connection ungrounded at the antenna end and ground the receiver end. The problem with that setup is that the coax shield can pick up noise, since it can act as part of the antenna. If you have a “radio quiet” location, this won’t matter, but few locations are free of man-made noise these days.

SWL Box

Matchbox Connections: A-Antenna, B-Secondary Ground, C-Primary Ground

Another configuration is to remove the short and ground the antenna side of the transformer (B). (This is the best connection to keep static charge from building up on your antenna.) Then, you can try grounding the receiver end or letting it float (no ground) to see which gives you the least amount of noise. A good way to test this is to tune in a relatively weak signal and see which configuration results in the best reception. Whatever you choose, there must be some sort of ground connection to stud B–even if just a counterpoise wire–on the matchbox or you’ll suffer severe performance degradation.

Wherever you make your actual ground connection, be sure to use at least a 6 foot ground rod. You can get these at your local hardware store or any big box home improvement store.

As always, I’m available for support if you need it. Just use the secure contact form.

73,
Ken W4KGH

Ground vs. counterpoise on matchbox

radiotowerA customer responded that he was using a “…direct to ground connection with a ground rod. The direct to ground connection seemed to [quiet] some of the extra noise on the receiver.” I assume that he had tried using just the counterpoise first and it was noisy.

If you are using the matchbox with a counterpoise or just relying on your coax to provide the counterpoise for RF and you notice the antenna seems noisy, try the ground rod method. Besides the potential noise reduction benefit, you’ll also provide a path to ground that will bleed off any static buildup on the antenna–a good safety feature.

As always, it it good to experiment.

73,
de W4KGH