Some antenna questions

[SpaceForceCmdr]

I have a telescopic antenna in my attic that's attached to a magnetic mount, and I was wondering about a few things. Do these types of antennas perform better than the non magnetic ones? I currently have it stuck on a metal pipe. If it's not attached to metal it doesn't seem to work as well (I guess because it's not grounded?). I know these telescopic whips aren't ideal for SW listening, but they do seem to be somewhat effective because the one on my portable SW radio works OK.

I'm limited to indoor antennas right now, so I'm wondering if there is a better option than a simple telescoping antenna. I plan on running a long wire the length of the attic, and then attaching that to the whip to see if I can improve reception. Since I like to listen all over the spectrum, I was thinking maybe I could put a discone antenna in the attic. Would it pick up any SW stuff at all? What if I attached the long wire to it when I was interested in listening to SW?

I know none of this is really optimal, but I'm just looking for some reasonable improvements

 

[prcguy]

A short antenna like 5ft tall is a very high impedance on VLF through most of HF. The whip connection on a portable SW receiver is high impedance and designed to work with a short whip. Stick the same whip on a length of 50 ohm coaxial cable and much of your signal will go away due to a huge mismatch of the high impedance antenna trying to feed the low impedance coax.

A length of wire like 30-50ft in the attic attached to a 9:1 balun feeding coax to your radio would be a much better antenna for SW.

 

[ka3jjz]

You really should try a loop in the attic. If you have the room, it should work a ton better than a mag mount and whip. You don't even need to get that expensive - many people are using the Chinese made MLA-30+ (found on fleaBay) with decent results. It's about USD50, last time I looked. There's even a FB group devoted to modifying this loop for better performance

Mike

 

[SpaceForceCmdr]

You really should try a loop in the attic. If you have the room, it should work a ton better than a mag mount and whip. You don't even need to get that expensive - many people are using the Chinese made MLA-30+ (found on fleaBay) with decent results. It's about USD50, last time I looked. There's even a FB group devoted to modifying this loop for better performance

Mike

That looks awesome, but I see it needs power. I guess a passive version wouldn't be as effective?

 

[prcguy]

Hey SpaceForceCmdr, you wouldn't happen to be in So Cal would ya?

 

[SpaceForceCmdr]

Nah, in OH.

 

[prcguy]

Ok, anyway the cheap active loop is something to consider and the power just runs up the coax, no extra wiring needed. Any antenna inside a house is subject to picking up lots of RF interference from stuff in the house and when I tested an active loop inside my house it was quite impressive.

Nah, in OH.

 

[ka3jjz]

And the nice thing here is that it's not a huge investment. If you find that the MLA30+ shows promise, then you can move to something like the W6LVP loops, et.al. Remember the point here is to experiment to find a good signal to noise ratio, not necessarily strong signals. This is a trap a lot of folks fall into when experimenting with an active loop. Mike

 

[KB2GOM]

Running a loop of insulated wire around the perimeter of your attic (if you can manage it) might improve your signal-to-noise.

I did this: Jock designs a Horizontal Room Loop to cope with reception issues

I am NOT claiming that it is an optimal solution, but it is better than the whip on my Satellit 800, and it was cheap to do. Depending on the logistics of your attic, it could be really annoying to place the wire.

KA3JJZ's suggestion for the MLA30+, I think, is a good one, and I am thinking of giving one a try.

 

[SpaceForceCmdr]

So, I ran a length of 20 gauge copper wire in a straight line, from one end my attic to the other. It's the short side of the house, so I'd say 25-30 ft long. I connected this to the end of a telescopic whip that' up there, and then that line feeds down into my room. I definitely get more signal than just the whip alone. It's bare copper wire. Not sure if it matters that it's not insulated?

My main issue at this point is the background noise. For example, I tuned in a station around 480o last night, and I could hear the voices, but the was a pulsing hum in the background that became very annoying. Every few seconds, the signal would raise and lower by at least 10 dB, and the volume of the low hum would go up and down, too. I guess this is just interference? I notice the same phenomenon if I turn on my portable and walk around the house. The signal fades in and out, and the low freq hum is there. It's one thing when there's just static, but the slowly pulsing signal with a bassy background hum is no fun to listen to.

 

[popnokick]

As was suggested in the first part of this thread of messages, use a loop antenna to minimize pickup of EMI / RFI (interference) from inside your house. There are loop recommendations in this thread and forum, as well as entire loop topic area in the RR Wiki.

 

[SpaceForceCmdr]

Is an active loop going to be better than passive? I would use it with my Eton Exec and also RSP1a SDR.