[Boatanchors] Boatanchors Digest, Vol 108, Issue 5
bonddaleena at aol.com
bonddaleena at aol.com
Fri Jan 4 14:03:51 EST 2013
A lot of great info here!
A couple of years ago, I acquired (leaglly!!) thousands of feet of brand new Comm-Scope CATV hardline. This stuff CANNOT allow water ingress and I have had zero problems with anything.... I still have rolls of 5/8", 7/8", 1 1/4" etc...
I have used it at several locations. I know that this was a question concerning receive, but.....
Right now, I use 5/8" CATV stuff for my tribander at 95' up
7/8 " for 6, 2 and 432. I use mast mounted preamps on 2 and 432.
I have a small machine shop and make my own CATV to coax connectors from 6061-T6 billet.
The built in antenna tuners on my HF and 6 M radios will instantly 'tune' the 75 ohm stuff to 1:1. Trying to make matching sections etc, to transform the 75 to 50 ohms is not worth the problems with connectors, etc.
I also use a lot of RG-6 and RG-59 to directly feed dipoles. Only problem there, is the bonding of the aluminum shield....
ron
N4UE
-----Original Message-----
From: boatanchors-request <boatanchors-request at mailman.qth.net>
To: boatanchors <boatanchors at mailman.qth.net>
Sent: Fri, Jan 4, 2013 12:00 pm
Subject: Boatanchors Digest, Vol 108, Issue 5
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Today's Topics:
1. antenna question (Gerry Steffens)
2. Re: antenna question (Bill Cromwell)
3. Re: antenna question (Jim Wiley)
4. Re: antenna question (J. Forster)
5. Re: antenna question (Al Klase)
----------------------------------------------------------------------
Message: 1
Date: Fri, 4 Jan 2013 07:21:05 -0600
From: "Gerry Steffens" <gsteffens at pitel.net>
To: <boatanchors at mailman.qth.net>
Subject: [Boatanchors] antenna question
Message-ID: <[email protected]>
Content-Type: text/plain; charset="us-ascii"
An acquaintance who is also a boatanchor collector/SWL/BCB DXer (and messes
with longwave a little bit) asked me the following antenna question. It has
been a while since I have sharpened up on antennas so I said I would ask the
wizards.
Wizards:
He recently moved from a plain old house to a quite new residence with metal
siding. He reports that reception has gone in the tank compared to his old
place. He has various radios scattered throughout the house and had
previously connected only a chunk of wire to most and received a good
quantity of signals. He also uses several McKay/Dymek active loop antennas
(one per radio) on some of the BCB radios. None of these work well in the
new place. He uses a McKay/Dymek (Stoner) outdoor active antenna (DA100D)
at his bench. The latter works very well. The DA100D has an amplifier at
the outdoor antenna and another inside at the bench. Output of the base
unit is RG58 cable to the receiver in use.
The local TV-DSL/internet provider has gone digital and recently came
through and replaced their old system box with a new one at the entry point
and ran CAT 5 cable from their new box to another "BOX" at each TV set and
computer, abandoning his 75 ohm analog distribution system which runs all
over the house. The question: Is there a good way to connect the active
antenna output which uses RG58, 50 ohm output to utilize the 75 ohm system
to get an antenna to his several radios and expect decent receiving
performance?
He came up with this as he was preparing to remove the old abandoned system.
He has decided that if he can't use the 75 ohm system, "Its gotta go!"
Frankly, he has more ambition than I as I would just let the old system
collect spider webs.
Gerry
------------------------------
Message: 2
Date: Fri, 04 Jan 2013 09:14:58 -0500
From: Bill Cromwell <wrcromwell at gmail.com>
To: Gerry Steffens <gsteffens at pitel.net>
Cc: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] antenna question
Message-ID: <1357308898.1968.5.camel at lancelot>
Content-Type: text/plain; charset="UTF-8"
Hi,
Your friend can buy adapters that will connect the old cables to the
RG-58 system connectors in either direction. I know...the radio stuff
was designed for 50 ohms and the old TV cable is 75 ohms. Close enough.
Other hams use surplus and recycled 75 ohm cable on their ham station
antenna all the time. Some of them are pumping 1500 watts of RF though
it. I haven't gone to those stations to verify and I never run more than
~100 watts myself. I have used 75 ohm cable with *impunity*. Tell your
friend yo GO for it.
73,
Bill KU8H
------------------------------
Message: 3
Date: Fri, 04 Jan 2013 05:16:05 -0900
From: Jim Wiley <jwiley at gci.net>
To: Gerry Steffens <gsteffens at pitel.net>
Cc: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] antenna question
Message-ID: <50E6E425.4010506 at gci.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
The 75-ohm distribution system may work just fine. The caveat has to do
with the "splitters". The cable itself will carry the signals just
fine, and with minimal loss. The small additional loss caused by the
(approximately) 1.4 to 1 SWR system when feeding a 50-ohm termination
(in this case one of his receivers) from a 75-ohm source will not be
noticeable at HF for receive signals. In all likelihood, the HF
receivers your friend has are unlikely to be precisely 50-ohms resistive
at their input terminals anyhow.
The splitters at each distribution point may be a problem, maybe not.
Depending on their internal circuitry, they may work well at MF and HF,
or they may not. There is no way to tell without testing or at least
trying them to see. If they work, with relatively low loss, then all is
well. If not, then you may have to look for some better quality units.
Some of the units designed for broad-band cable systems work well at HF
and MF, others do not. Most types designed for just TV antenna
distribution will probably not work well. Again, try them and see.
If the splitters in place do not work well (characterized by very low
signals), then you can try several alternatives. (1) try direct
connection (a straight direct-connected coaxial tee fitting, with no
splitter). If the various receivers don't try to talk to each other (HF
oscillator interference) a simple hookup like that may be all you need.
(2) Try resistive splitters. These will have 10 to 15 dB loss, but
that may be acceptable, considering that you are working from an active
receiving antenna that has some gain that can overcome losses down the
line, and resistive splitters are inherently very broad-band. (3) Roll
your own couplers from ferrite toroidal transformers - a reasonably easy
process that is not expensive, and works well. Suitable designs can be
found on line or in many of the later handbooks. You will most likely
want a hybrid-type coupler that has about 6 dB insertion loss.
If I was dong this, I think I would prefer the resistive splitters over
building hybrid transformers.
The fact that he cannot receive signals well inside the building is
almost certainly due to the fact that the metal siding, particularly if
well bonded, is acting like a shield and preventing HF and MF signals
from getting inside the structure. MF and HF signals have too large a
wavelength, and the holes (doors and windows) in the structure are not
large enough to admit the signals. This is the same effect that causes
AM broadcast signals to fade when driving under overpasses or inside
metal bridges (or tunnels) but FM signals continue just fine. The
roughly 3-meter wavelength of the FM signals "fit" though the holes in
the structure, the several hundred meter wavelength of the AM BC signals
does not.
He will definitely need some sort of outside antenna, either amplified
or perhaps just a plain wire. If he wants to get fancy, he can install
a distribution amplifier from the main antenna to his former CATV
distribution system to boost signals as needed. Needless to say, he
will not be able to transmit through such a hookup, but from what you
say, he seems to interested in receive only.
In any case, I would leave the installed 75-ohm cable system in place.
One never knows when such a thing may come in handy.
- Jim, KL7CC
On 1/4/2013 4:21 AM, Gerry Steffens wrote:
> An acquaintance who is also a boatanchor collector/SWL/BCB DXer (and messes
> with longwave a little bit) asked me the following antenna question. It has
> been a while since I have sharpened up on antennas so I said I would ask the
> wizards.
>
> Wizards:
>
> He recently moved from a plain old house to a quite new residence with metal
> siding. He reports that reception has gone in the tank compared to his old
> place. He has various radios scattered throughout the house and had
> previously connected only a chunk of wire to most and received a good
> quantity of signals. He also uses several McKay/Dymek active loop antennas
> (one per radio) on some of the BCB radios. None of these work well in the
> new place. He uses a McKay/Dymek (Stoner) outdoor active antenna (DA100D)
> at his bench. The latter works very well. The DA100D has an amplifier at
> the outdoor antenna and another inside at the bench. Output of the base
> unit is RG58 cable to the receiver in use.
>
> The local TV-DSL/internet provider has gone digital and recently came
> through and replaced their old system box with a new one at the entry point
> and ran CAT 5 cable from their new box to another "BOX" at each TV set and
> computer, abandoning his 75 ohm analog distribution system which runs all
> over the house. The question: Is there a good way to connect the active
> antenna output which uses RG58, 50 ohm output to utilize the 75 ohm system
> to get an antenna to his several radios and expect decent receiving
> performance?
>
> He came up with this as he was preparing to remove the old abandoned system.
> He has decided that if he can't use the 75 ohm system, "Its gotta go!"
> Frankly, he has more ambition than I as I would just let the old system
> collect spider webs.
>
> Gerry
>
>
>
> ______________________________________________________________
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>
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> ** For Assistance: dfischer at usol.com **
>
>
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>
------------------------------
Message: 4
Date: Fri, 4 Jan 2013 07:33:14 -0800 (PST)
From: "J. Forster" <jfor at quikus.com>
To: "Gerry Steffens" <gsteffens at pitel.net>
Cc: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] antenna question
Message-ID: <55166.12.6.201.2.1357313594.squirrel at popaccts.quikus.com>
Content-Type: text/plain;charset=iso-8859-1
The difference between 50 and 75 Ohms is pretty much irrelevant for
receiving HF unless you are trying to squeeze out the last droplett of
performance.
That said, there are a few things to consider:
If the system has a distribution amp it may not be any good for HF/LF.
If the system uses power splitters, they will likely not be any use.
If the system uses 75 Ohm BMCs, they will need to have the correct mate.
Essentially, the guy will be converting his setup to look like a
multicoupler serving a bunch of receivers.
-John
==========
> An acquaintance who is also a boatanchor collector/SWL/BCB DXer (and
> messes
> with longwave a little bit) asked me the following antenna question. It
> has
> been a while since I have sharpened up on antennas so I said I would ask
> the
> wizards.
>
> Wizards:
>
> He recently moved from a plain old house to a quite new residence with
> metal
> siding. He reports that reception has gone in the tank compared to his
> old
> place. He has various radios scattered throughout the house and had
> previously connected only a chunk of wire to most and received a good
> quantity of signals. He also uses several McKay/Dymek active loop
> antennas
> (one per radio) on some of the BCB radios. None of these work well in the
> new place. He uses a McKay/Dymek (Stoner) outdoor active antenna (DA100D)
> at his bench. The latter works very well. The DA100D has an amplifier at
> the outdoor antenna and another inside at the bench. Output of the base
> unit is RG58 cable to the receiver in use.
>
> The local TV-DSL/internet provider has gone digital and recently came
> through and replaced their old system box with a new one at the entry
> point
> and ran CAT 5 cable from their new box to another "BOX" at each TV set and
> computer, abandoning his 75 ohm analog distribution system which runs all
> over the house. The question: Is there a good way to connect the active
> antenna output which uses RG58, 50 ohm output to utilize the 75 ohm
> system
> to get an antenna to his several radios and expect decent receiving
> performance?
>
> He came up with this as he was preparing to remove the old abandoned
> system.
> He has decided that if he can't use the 75 ohm system, "Its gotta go!"
> Frankly, he has more ambition than I as I would just let the old system
> collect spider webs.
>
> Gerry
>
>
>
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
------------------------------
Message: 5
Date: Fri, 04 Jan 2013 11:24:17 -0500
From: Al Klase <ark at ar88.net>
To: BOATANCHORS at MAILMAN.QTH.NET
Subject: Re: [Boatanchors] antenna question
Message-ID: <50E70231.8060601 at ar88.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Gene,
Take a look at my site for some inspiration.
http://www.skywaves.ar88.net/ANTENNA/antsys.htm
You may need some sort of broad-band amp if you split more that 2 or
three times. Count a three dB loss for each 1:2 splitter.
Al
On 1/4/2013 8:21 AM, Gerry Steffens wrote:
> An acquaintance who is also a boatanchor collector/SWL/BCB DXer (and messes
> with longwave a little bit) asked me the following antenna question. It has
> been a while since I have sharpened up on antennas so I said I would ask the
> wizards.
>
> Wizards:
>
> He recently moved from a plain old house to a quite new residence with metal
> siding. He reports that reception has gone in the tank compared to his old
> place. He has various radios scattered throughout the house and had
> previously connected only a chunk of wire to most and received a good
> quantity of signals. He also uses several McKay/Dymek active loop antennas
> (one per radio) on some of the BCB radios. None of these work well in the
> new place. He uses a McKay/Dymek (Stoner) outdoor active antenna (DA100D)
> at his bench. The latter works very well. The DA100D has an amplifier at
> the outdoor antenna and another inside at the bench. Output of the base
> unit is RG58 cable to the receiver in use.
>
> The local TV-DSL/internet provider has gone digital and recently came
> through and replaced their old system box with a new one at the entry point
> and ran CAT 5 cable from their new box to another "BOX" at each TV set and
> computer, abandoning his 75 ohm analog distribution system which runs all
> over the house. The question: Is there a good way to connect the active
> antenna output which uses RG58, 50 ohm output to utilize the 75 ohm system
> to get an antenna to his several radios and expect decent receiving
> performance?
>
> He came up with this as he was preparing to remove the old abandoned system.
> He has decided that if he can't use the 75 ohm system, "Its gotta go!"
> Frankly, he has more ambition than I as I would just let the old system
> collect spider webs.
>
> Gerry
>
>
>
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
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--
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/
------------------------------
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