RadioBanter - View Single Post - What's a better HF receive-only antenna: MFJ-1024 or a loop?

May 12th 05, 07:55 PM

wrote:

Hi,

I need broadband (2MHz - 30MHz) receive-only capability. I will be
connecting the antenna to a system that can stare at 10 MHz of RF
spectrum simultaneously. I have very limited space and almost no
antenna experience.

I've been told to look for a loop antenna. I stumbled across the
MFJ-1024 active antenna.

What's the best choice for my application? I want to hear very weak
signals.

I have limited time available to do the install. I'll gladly spend more
money to have less hassle and a greater probability of success.

John

Hi

I really think we need more information about how you define "limited space" and
how much easy work you're willing to do to give you a good answer.

Active antennas amplify everything they pick up including your neighbors lamp
dimmer, your crt computer monitor and possibly any VCR's you might have. If
you're gonna get one, I suggest installing it away from the house.

If one antenna is 10 feet away from a noise source and one is 5 feet from it,
the farther one will get 4x less noise. Change that to 50 feet and 5 feet and
the farther one gets 100x less noise. (square of the distance)

With modern radios, signal to noise level is almost always more important than
signal strength.

Loop antennas are often designed to be tuned for each frequency. If you're
looking at 10mhz of spectrum all at once, you don't want one with this feature.

An advantage loops have is they don't pick up as much local rfi (noise) as most
other types. Dipole antennas are also relatively immune to local noise.

Someone else mentioned the Wellbrook Loop. It's an active loop. I've never
used one, but they're highly respected, and next time I want a "transportable"
antenna with at least a couple weeks notice I'll probably buy one. (you have to
order them from England) It's probably a "safe" choice, and I'd expect it to
out perform the MFJ because the loop won't pick up as much noise as the whip.

But if you can put 30 or more feet of wire 50 or more feet away from the house
with an impedance matching transformer and run coax underground to the house,
that'll probably work well for you too. It's not rocket science, and folks here
can give you all kinds of tips to get it going quickly.

I have a 60' random wire about 225 feet away from the house. It works
incredibly well. Other than getting the trench put in, (I hired someone for
that) it was a one morning job.

For my vacations and camping radio, I use a broadband active whip made with
milspec components. It works well too - but I use it away from devices that
cause rfi.

Good luck.

Mark