HFU HF Underground
Technical Topics => Equipment => Topic started by: RCCI on January 24, 2013, 0244 UTC
-
OK a brief history... back when I had more money (1980's) I used a FRG8800, an Antenna Supermarket Trapped Dipole antenna, a MFJ amplified preselector, and a Yaesu FRT7700. With the trapped dipole being what it was, the FRT7700 and the amplified preselector had minimal improvement in reception. Sadly I sold the equipment years ago, with deep regret.
At this point, I use a Kenwood R1000 with a simple 30' longwire (I rent so a new antenna is not an option, costwise and real estatewise. That's it. Reception is fairly good, but somehow I feel that it could be better.
I have read a number of opinion on the net including the lengthy analysis of using a preselector over an antenna tuner. Some SWL's prefer a tuner, some prefer the preselector.
I have been eyeing several pieces, a MFJ 1046 Passive Preselector, an MFJ 956 antenna tuner, the FRT7700 (again)
I am just inquiring what others use at this time, and what varying degrees of success you have had. Do you use a Preselector, an Antenna Tuner, Both? If so what brand??
Any suggestions? Tight budget. TIA ...Steve
-
Preselector == antenna tuner, but denotes receive only.
They are simple devices. If you have a junked AM radio, you probably have the parts to make one yourself :)
Peace!
-
I have the MFJ 1045C that I have used with the DX-390 and a 15 foot piece of insulated wire thumb tacked around the ceiling of my room. Both radio and preselector operated off batteries. This was what I used during thunderstorms when I had to disconnect the outside antennas and power down other radios. It worked quite well in tuning in pirates. I remember switching from an R-75 and a very long wire antenna mounted really high above the ground to this setup while listening to Ground Zero Radio in the middle of a massive storm. The signal didn't drop off at all. I haven't used it in years, but when I did it worked well. It always improved reception - sometimes just a little, and sometimes quite a lot. I only used it with the DX-390 portable, so I don't know this for a fact - but I think the smaller portables benefit more from it's use than a higher end tabletop would.
:) just my experience
-
One last question.... Could or does anyone run an antenna tuner AND a preselector in a SERIES?. For example... run the outside line to a FRT7700 (passive) antenna tuner directly to a (passive) preselector? I never had tried it with my old system.
Should the ANT TUN. and PRESEL. just stand alone? ...as a series... sound plausible. Feedback?
-
Yeah those tight antenna locations are tough but not impossible.
Tell us a little more about your outside environment such as;
Could you double back the wire in some direction to increase length?
Are you on the first floor or??? and if so could you, at some discreet time,
bury a little wire? The reason I ask is that there may be an answer in a
low noise buried wire coupled with a strong preamp. Just a thought as I
have used one with good results. Noised could be a big factor in your
ability to hear more stations.
Do you have in the rental a large room that could accommodate a loop?
Even a small loop with a good preamp may be an option.
So a little more on your outside environment would help.
weaksigs
-
One more suggestion - a site that has some good info
Here's one on SW antenna as experienced by one gent.
http://www.qrp.pops.net/swl-ant.asp
Have fun Reading-
WEAKSIGS
-
weaksigs...
The antenna I use is 30'14 gauge speaker wire running off the top of a porch 9-10 feet high and sloaping slightly downward to a pine tree ending at 8' high.. It's 70% in front of the house (about 7") and runs south to north. It's totally clear reception from signals coming from the east and south and most of the north. Signals from the west are picked up with about 9' clearing the house from the pine tree to the front of the house. I do pick up hams periodically from CA.
Best HAM signals come in from Ohio, Michigan and out east. Some reception from Illinois. I don't use coax as a feedline, just additional speaker wire. It's not grounded, in the sense of a wire running off the receiver to a cold water pipe or a grounding rod. The receiver is in a bedroom. with my computer and radio perched on a table next to the window. The window opens out to the porch, so the feedwire is only about 6'. The landlord would probably take a dim view of a a 6' rod going into the ground along the side of the house. I have heard of copper sheeting on the floor as a ground, and artifical grounds. ...Steve
For SSB and CW, I am also looking into a DSP, (The radio Shack DSP-40)
When I had my Frog8800 I used a trapped dipole up about 24' running East and West., back in the 80's. (different house) With the preselector, it was amplified and noticed only a slight difference. The same with the FRT7700. I'm guessing with the 6 traps, they did their job.
BTW thanks for the link... It was interesting reading!
-
I've got one of the MFJ 1045's that LCee has. They're great if you've got to run a compromise antenna into a portable radio. Cuts down on images and peaks signals.
-
I have a homebuilt antenna tuner made from a couple AM radio tuner caps and a homebuilt wound coil. It reduces images on my DX-160, but aside from that, there's little improvement. I generally I don't use any tuners with my wire antennas; if I want better signals I try to improve the actual antenna.
I think preselectors are a good idea with some radios. The Yaesu FRG-7 came with one built in to the radio. Worked very well.
-
I use a grove Tuner 4a with my my attic 66' off center dipole antenna with my JRC 535d. It seems to help on weak signals.Have plans on putting up an outside antenna as i have space to do so . I n any event the Grove gives a couple options amp on or pre select..
-
Well.... after much experimenting I seemed to have come up with a pretty satisfying combination for the R1000. The speaker wire coming in from the window, is banana clipped to a 4 foot section of RG6 coax which is fed into the MFJ 901B. Using 2 - 2 foot jumper coax cables, one goes from the 901B into a MFJ 956 and the second from the MFJ 956 into radio coax antenna receiver socket. I found that the RG6 being so well shielded, reduced the noise level by 2db. Really pulling out the faint stations now..... (Before that, the Kaito KA1103 portable was "out-listening" the R1000)
I tried amplified versions, and found the passive much easier and better hearing than the amplified.
As the one guy on Duck Dynasty says... happy - happy - happy.
-
An antenna tuner is interacting with capacitance and/or reactance to improve matching with non-resonant antennas. That said, HF has a relatively high noise floor, so an antenna tuner might do little to improve overall S/N for an otherwise broadbanded SWL antenna setup. YMMV, of course, especially depending upon the antenna being used.
A preselector is essentially a bandpass device. I typically use one to help with signal selectivity when using portables with outdoor antennas. A decent preselector can go a long way to cleaning up an easily overloaded receiver frontend.
-
I use Mizuho SX-3 & SX-59 Preselctors. They are old & rare but well worth the effort to fond one. The SX-59 I have has worked flawlessly for well over 20 years. I purchased it long ago from the now efunct Gilfer Shortwave in Park Ridge NJ.