Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Date: Wed, 08 Nov 1995 05:13:42 GMT
Organization: Internet Access Cincinnati 513-887-8877
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
There have been several posts recently regarding antennas for apartment dwellers etc.
For receiving antennas the lengths are not critical. Generally the more metal(wire) one puts up the better.
When I had limitted space in an apartment I tried several techniques which I can recommend.
1) I attached a weight(metal nut) to a length of 'transformer'(fine) wire, and hung it out my apartment window.
2) At another location I used the same attachment and tossed the wire over the top of the apartment roof.
THese were never detected and worked fine. They are also very cheap.
Try to get the wire antenna as high as possible and as far away from objects as possible.
In my opinion I would NOT buy an 'active antenna' except, MAYBE, as a last resort.
Basically, an active antenna uses a small antenna(typically) and amplifier which amplifies all the signal AND NOISE, that the small antenna captures.
With an active antenna one is gambling that the signal/noise ratio of the active antenna amplifier is better than the first amplifier stage of the rcvr.
Not a bet I am willing to make at $50 to $100 for an active antenna. Of course the active antenna could overload the
front end of the rcvr, again CAUSING reception problems.
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Another simple antenna for indoor use. Use fine wire (to make it less noticeable).
Put some push tacks along the wall, near the ceiling. Use the tacks to hold the
wire up. Just wrap the wire around each tack once and go to the next tack.
Thanks to Mr.Newell for responding to my article. I will
respond to his comments here.
>>For receiving antennas the lengths are not critical.
>
>WRONG: Length is ALWAYS critical.
>================================
We are talking about 'Limitted Space Antennas' here, where a full size
antenna is not possible.
Also, the discussion here is of one antenna for SWL listening.
>> Generally the more metal(wire) one puts up the better.
>
>WRONG AGAIN: If your a fan of the 20 or 15 Meter Band, you obviously
>would not just stick a 100 foot length of wire out your window. You
>would probably cut a half-wave dipole, where yes, the length is critical.
Again we are talking 'Limitted Space Antennas'. If
I were a fan of the 20 meter band and I had a 33foot dipole
(or maybe add more elements), then I would
want to rotate it, then I might be interested in other bands, so I
either add traps, add another antenna, put it up high on a tower...
Again we are talking 'Limitted Space Antennas', e.g. an apartment dweller.
The discussion here is of one antenna for SWL listening, NOT devoted to
ONE band.
>
>>In my opinion I would NOT buy an 'active antenna' except, MAYBE, as a >last resort.
>
>You obviously have never used an active. The actives of my design
>and construction, using MOSFET and BiPolar transistors, outperform
>longwires up to 125 Feet ( Inverted-L ) . They have a better noise
>figure and a much sharper Q.
I think you are agreeing with me here. I said I would not buy one, and you
said you designed and built your own. I would only use a proven design.
>>Basically, an active antenna uses a small antenna(typically) and >amplifier which amplifies all the signal AND NOISE, that the small >antenna captures.
>
>Explain yourself. ALL what noise? All the noise on that frequency
>and 10 to 50 Khz on each side of the desired frequency ?? With
>an active you are tuning one frequency with the receiver and
>tuning with the preselection tuned circuit as well. Noise and
>disturbances as little as 7 Khz away can re reduced substantially
>through this process.
>
>>With an active antenna one is gambling that the signal/noise ratio of >the active antenna amplifier is better than the first amplifier stage >of the rc
>
>By and large, a 2 transistor Active w/ a well designed tuned RF
>stage will not contribute that much internal noise.
>
>>Not a bet I am willing to make at $50 to $100 for an active antenna.
>> Of course the active antenna could overload the
>>front end of the rcvr, again CAUSING reception problems.
>
>Not if used properly.
The crux of the issue with amplifiers before your rcvr is whether the amp has a
lower noise figure than the rcvr. A systems noise figure is primarily determined
by the first gain stage noise figure. So if the rcvr front end was WORSE
than the external amp
then I would go with the external amp. But I want to start with
a rcvr with a good front end!! To often people think that an external amp will
make up for a crummy antenna. The moral of the story is start with a good rcvr!
>snip<
Below 3Mhz tuned loop antennas work well for DXing (in fact because of the
characteristics of the band simple short wire antennas do not work well at all).
Loop antennas can be made any size
desired. They are very directional, eliminating interference. They are
basically a loop(inductor) and a capacitor, forming a tuned circuit. Mr.
Newell has a design for one. Maybe he would post it and share it for all.
Subject: Re: National Communications System at Warrenton, VA - Check it Out!! [and as long as you are at it, just what is going on in Mercersberg PA and Boonsboro MD??]
Date: 22 Nov 1995 15:09:53 GMT
Organization: Syracuse University, Syracuse NY, USA
