Thanks for all who responded thus far (and sorry to be such a wellspring of
newbie questons).

Yes, I must confess that there is no lightning arrestor installed as of yet!
I was aware that one should install such a device at the time I put up the
antenna, but I didn't have one handy, nor did I feel the need to invest in
one. I was thinking that in the late fall/winter we really don't get any
lightning here (north-east PA) and therefore I wouldn't really need a
lightning arrestor until the Spring. I'm sure I'm probably wrong on this,
though, as it was mainly a product of my Scots heritage getting the best of
me.

I guess it would be helpful to include some more specifics about what radios
Im trying to feed with this antenna. Thus far, I have accumulated an
A****er Kent "big box" Model 20, an A****er Kent 55-C (chassis only), an
RCA Radiola 18, and a homebrew regen. This is my latest project.

It uses a '36 screen grid tube as detector and a 6F8G as dual-stage audio
driving a loudspeaker through an overly large Hammond OPT. So far I've only
wound a coil for BC band and this thing works amazingly well. I plan on
making some smaller coils for short wave (hopefully the solar storm stuff
wont be long in staying).

I also have future plans for a Grigsby-Grunow that was given to me to fix
up, but it's on the distant horizon as of yet.

So far nobody has complained about the large pile of radio-related crap in
the sun porch, but Im sure it's a matter of time. I will probably have to
route the antenna lead-in through a wall or two and around some bends and
twists to get it into the workshop in the basement. I guess I was assuming
I should use coax for this, but apparently not, from what everyone here is
saying. I'm not as concerned about noise as I am about possible signal
loss. Is this something to even be concerned about with a plain old
insulated stranded wire lead-in routed through walls and such?

I'm still new at this RF stuff (being a relatively recent convert from the
realm of "AF"), so please bear with me, and thanks for all the helpful tips
and suggestions!


Dave

Bob, is this something I could possibly be able to use in this application?
Where does one find such high-impedance coax? As an alternative, would it
be possible to put an active device up near the antenna that would act as a
buffer to feed a low-impedance line?

Dave


"Bob Lewis (AA4PB)" wrote in message
...
If the antenna is the typical end-fed wire then the impedance will be
very high. Most AM radios have a high impedance input designed to
match a random wire like that. If you use coax, the capacitance of the
coax (center conductor to shield) will essentially short most of the
signal to ground and little will get to the receiver. If you've ever
opened up the coax used on car radios you'll find that it is a special
high impedance coax. A small wire fits loosly thru an insulated tube
with the shield around the outside. This keeps a relatively large
spacing between the center conductor and the shield in order to
minimize capacitance.

Bob, is this something I could possibly be able to use in this application?
Where does one find such high-impedance coax? As an alternative, would it
be possible to put an active device up near the antenna that would act as a
buffer to feed a low-impedance line?

Dave


"Bob Lewis (AA4PB)" wrote in message
...
If the antenna is the typical end-fed wire then the impedance will be
very high. Most AM radios have a high impedance input designed to
match a random wire like that. If you use coax, the capacitance of the
coax (center conductor to shield) will essentially short most of the
signal to ground and little will get to the receiver. If you've ever
opened up the coax used on car radios you'll find that it is a special
high impedance coax. A small wire fits loosly thru an insulated tube
with the shield around the outside. This keeps a relatively large
spacing between the center conductor and the shield in order to
minimize capacitance.

Hi,
David wrote:

Yes, I must confess that there is no lightning arrestor installed as of yet!

it was mainly a product of my Scots heritage getting the best of me.

Sounds familiar. Actually a lighting arrestor isn't worth much,
and I'd suggest a large knife switch directly between the lead-in and
ground.

Your present antenna is ideal for broadcast reception since, as has
been mentioned, most antique radios were designed with this sort of
antenna in mind. Extending the lead-in to the basement will simply
make it work better. The vertical part of the lead-in catches most of
the signal. Keep it as far from power lines and noise sources as
possible. If your ground is now farther away, you may lose some
efficiency; my ground is a driven well in the basement.

On short wave, things are different. I've used my inverted-L for
short wave too, but never compared it directly against another
antenna.

Cheers, Alan

Hi,
David wrote:

Yes, I must confess that there is no lightning arrestor installed as of yet!

it was mainly a product of my Scots heritage getting the best of me.

Sounds familiar. Actually a lighting arrestor isn't worth much,
and I'd suggest a large knife switch directly between the lead-in and
ground.

Your present antenna is ideal for broadcast reception since, as has
been mentioned, most antique radios were designed with this sort of
antenna in mind. Extending the lead-in to the basement will simply
make it work better. The vertical part of the lead-in catches most of
the signal. Keep it as far from power lines and noise sources as
possible. If your ground is now farther away, you may lose some
efficiency; my ground is a driven well in the basement.

On short wave, things are different. I've used my inverted-L for
short wave too, but never compared it directly against another
antenna.

Cheers, Alan

David Forsyth wrote:
Bob, is this something I could possibly be able to use in this application?
Where does one find such high-impedance coax? As an alternative, would it
be possible to put an active device up near the antenna that would act as a
buffer to feed a low-impedance line?

Dave

The trick in this recommendation is that the car radio feedline is a
specific length (a few feet)and its capacitance is taken into account.

-Bill




"Bob Lewis (AA4PB)" wrote in message
...

If the antenna is the typical end-fed wire then the impedance will be
very high. Most AM radios have a high impedance input designed to
match a random wire like that. If you use coax, the capacitance of the
coax (center conductor to shield) will essentially short most of the
signal to ground and little will get to the receiver. If you've ever
opened up the coax used on car radios you'll find that it is a special
high impedance coax. A small wire fits loosly thru an insulated tube
with the shield around the outside. This keeps a relatively large
spacing between the center conductor and the shield in order to
minimize capacitance.

David Forsyth wrote:
Bob, is this something I could possibly be able to use in this application?
Where does one find such high-impedance coax? As an alternative, would it
be possible to put an active device up near the antenna that would act as a
buffer to feed a low-impedance line?

Dave

The trick in this recommendation is that the car radio feedline is a
specific length (a few feet)and its capacitance is taken into account.

-Bill




"Bob Lewis (AA4PB)" wrote in message
...

If the antenna is the typical end-fed wire then the impedance will be
very high. Most AM radios have a high impedance input designed to
match a random wire like that. If you use coax, the capacitance of the
coax (center conductor to shield) will essentially short most of the
signal to ground and little will get to the receiver. If you've ever
opened up the coax used on car radios you'll find that it is a special
high impedance coax. A small wire fits loosly thru an insulated tube
with the shield around the outside. This keeps a relatively large
spacing between the center conductor and the shield in order to
minimize capacitance.

David Forsyth wrote:

Thanks for all who responded thus far (and sorry to be such a wellspring of
newbie questons).

Yes, I must confess that there is no lightning arrestor installed as of yet!
I was aware that one should install such a device at the time I put up the
antenna, but I didn't have one handy, nor did I feel the need to invest in
one. I was thinking that in the late fall/winter we really don't get any
lightning here (north-east PA) and therefore I wouldn't really need a
lightning arrestor until the Spring. I'm sure I'm probably wrong on this,
though, as it was mainly a product of my Scots heritage getting the best of
me.


Do yourself a favor: at the end of your antenna (inside
the house) install a neon bulb and a 100K resistor in
series, connected between the antenna and ground.
Then, on a windy day, go watch the bulb.

You can make your own static discharge unit:

-----------\ /--------------
Copper \ / Copper
Strip / \ Strip
-----+-----/ \-----+--------
| |
+---/\/\/\/-----+
100K

The points on the copper strips need to be sharp, not
blunt, at the gap.

Wire one strip to ground with #10 or larger copper wire,
and the other strip to the antenna. Set the gap between
the copper strips as narrow as you can. Solder a 100K
resistor across the copper strips.

David Forsyth wrote:

Thanks for all who responded thus far (and sorry to be such a wellspring of
newbie questons).

Yes, I must confess that there is no lightning arrestor installed as of yet!
I was aware that one should install such a device at the time I put up the
antenna, but I didn't have one handy, nor did I feel the need to invest in
one. I was thinking that in the late fall/winter we really don't get any
lightning here (north-east PA) and therefore I wouldn't really need a
lightning arrestor until the Spring. I'm sure I'm probably wrong on this,
though, as it was mainly a product of my Scots heritage getting the best of
me.


Do yourself a favor: at the end of your antenna (inside
the house) install a neon bulb and a 100K resistor in
series, connected between the antenna and ground.
Then, on a windy day, go watch the bulb.

You can make your own static discharge unit:

-----------\ /--------------
Copper \ / Copper
Strip / \ Strip
-----+-----/ \-----+--------
| |
+---/\/\/\/-----+
100K

The points on the copper strips need to be sharp, not
blunt, at the gap.

Wire one strip to ground with #10 or larger copper wire,
and the other strip to the antenna. Set the gap between
the copper strips as narrow as you can. Solder a 100K
resistor across the copper strips.

Hi,

There is no simple answer to your problem as the impedances
and frequency range involved are too great. However, as you are
not intending to use the antenna to transmit with, take a look at
this site and do a search on "LONG WIRE BALUN".

http://www.maplin.co.uk/

If you are in the U.S. I am sure that there will be an
equivalent item around somewhere. It is even possible that there
is a design for one of these out on the net.

The device is mis-named really and should be called something
like an UNUN. Of course it is a kludge but what the hell as it
should be better than a single wire or coax feed from your
basement.


Cheers - Joe, G3LLV