Single wire antenna has stray voltage- solved - Printable Version
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+--- Thread: Single wire antenna has stray voltage- solved (/showthread.php?tid=16685)
Single wire antenna has stray voltage- solved - jcassity - 05-21-2017
I have a random wire on glass insulators of all in about 300' outside and the highest point is i guess 55'.
I have in the garage a hallicrafters S-38d, inside the house i have a Philco 46-1226.
Hallicrafters has A1, A2 & G terminations and there is an S shaped link bonding A2 & G together.
On the Philco i think dad used a wire to bond #2 and #3 together but i took that out cause the wire was corroded a tad.,, i did not put it back and i get good reception.
so.... to yesterday.................
I run a wire out from the Philco out to my existing random antenna wire. While touching the outside antenna im getting shocked.
- the hallicrafters is plugged into the outlet and is in the off position and is tied to my outside antenna during the time i am getting shocked. I isolate the hallicrafters from the outside antenna then verify the source of my getting shocked is from the hallicrafters,, and not the outside antenna. Confirmed YES the source is from the Hallicrafters.
The shock i get is more like a low voltage "sting" so to speak.,,
I look on the back of the hallicrafters and the S jumper is bonding A2 and G together.
I remove undo the S jumper , reconnect the outside antenna and the power up the hallicrafters and verify that i still have all good reception on bands 1 through 5.
I go back out to tie the philco to the outside antenna and no more stay voltage... and all is well for two radios tied to the same antenna.
What the heck is going on when a radio has A2 & G bonded,, it seems there is an injection of voltage on the antenna when a jumper is installed yet the Hallicrafters was in the off powerd down state.
do i stand a chance of putting both my radios at risk by not having the jumper?
I like the idea of having one antenna available for rado use no matter how many radios i have.
RE: Single wire antenna,- What the heck is going on here - David - 05-21-2017
I never have 2 radios hooked up to the same ant at the same time. You might reverse the plug on the S-38 and see if the problem goes away. Your S-38 may have the hot side of the power plug going to the chassie. Please be careful!!!! David
RE: Single wire antenna,- What the heck is going on here - WallaceRoger - 05-21-2017
That is weird... If I had multiple radios I'd also like to be able to run them all to the same antenna... for example a roof aerial.
RE: Single wire antenna,- What the heck is going on here - Radioroslyn - 05-21-2017
What you would want to do is use a rotary switch to select radio is going to your ant. If you don't you can have shock issues, one set nulling out the reception of the other, and if more than one is on at the same time my may pick up the local oscillator of one of the sets. This is if you connect all ant leads of your set in parallel.
RE: Single wire antenna,- What the heck is going on here - jcassity - 05-21-2017
(05-21-2017, 04:08 PM)David Wrote: I never have 2 radios hooked up to the same ant at the same time. You might reverse the plug on the S-38 and see if the problem goes away. Your S-38 may have the hot side of the power plug going to the chassie. Please be careful!!!! David
s-38 is interally updated and upgraded to include a polarized plug. it has a chassis that that holds all the electrical parts and an isolated exterior chassis.---, but yes i thought of that also but remembered i did change the plug.
RE: Single wire antenna,- What the heck is going on here - jcassity - 05-21-2017
Terry,
i thought about nulling signals like if im on talk radio 960 on the philco and i tune to 960 in the garage on the hallicrafters,, if they both are on there would be a problem. Only one radio will ever be on at one time. I did test with both radios on by doing a random AM station on the philco and a different AM station on the S-38, no issues.
what i dont understand is what was that voltage?
also right now without jumpers from G and A2 on both radios, i dont have an issue so both are tied to the antenna.
i just wondered where this voltage was coming from,, like the filter caps or something? i dont see how on both diagrams for the hallicrafters or the Philco a path for current flow through the anenna components and parts.
I need to see if the philco does the same thing if i put a jumper on antenna screw 2 and 3 and leave the random wire on #1.
RE: Single wire antenna,- What the heck is going on here - Radioroslyn - 05-22-2017
On the S 38 there is ac leakage (normal) from B- to chassis ground because of the line filter cap (from the ac line to B-) and cap and it's parallel resistor connected from B- to chassis ground. If you look at the ant circuit the bottom end of the ant coils there connected back to the chassis through a cap which couples some ac to ant connection.
Trade your S 38 in for a set with a power transformer and you won't have these ground and shock issues. This a post war entree level set, for what it is it has a decent design BUT it's still a pig with lipstick.
RE: Single wire antenna,- What the heck is going on here - jcassity - 05-22-2017
simulated the same conditions on the Philco, no stray voltage.
without antenna straps installed on either radio, both can operate without issues on the same antenna.
so,, i will not have a strap on the hallicrafters which was producing low voltage leaking.
all is well,
problem solved
RE: Single wire antenna has stray voltage- solved - Ron Ramirez - 05-22-2017
I would suggest using a small capacitor, around .001 uF will do, between the antenna terminal of the radio and the actual longwire antenna. This will keep any voltage from your AC-DC Hallicrafters off the longwire without reducing the sensitivity of the input. As Terry (Radioroslyn) has mentioned, it is not a good idea to use the same longwire on more than one radio simultaneously.
RE: Single wire antenna has stray voltage- solved - jcassity - 05-22-2017
Thanks Ron,
i removed the strap on the S-38 and have no more stay voltage,, still use a cap in series with the long antenna wire?
RE: Single wire antenna has stray voltage- solved - jcassity - 05-24-2017
I am considering the rework of my long wire antenna,, and have a selector switch installed because even though i dont see an issue now,, doesnt mean what ive been told should be ignored, im sure there are good experineces to warrant a switch,, lightning for one is something that would bring both sets into one commmon point taking them out.
my switch is on/off/on for two sets on a rotary able to pick up to 8 contacts,,, something spare i had lying around.
what i want to know is with a single wire antenna, has anyone made the "VERY TOP" of the long wire adjustable 360deg as to point it?
before i start in on something i want to compare whats been done so i dont spin my wheels and waste time.
for some reason the cap i was told to add reduced volume capability
RE: Single wire antenna has stray voltage- solved - David - 05-24-2017
Joe Carr has written many books on ants, great reading material http://www.ea1uro.com/pdf/Practical%20AntennaHandbook%20vol%204.pdf Enjoy David
RE: Single wire antenna has stray voltage- solved - Warren - 05-24-2017
It takes more than to point the "top" of a wire to make an antenna directional so you can point it where you want. It has to be shaped a certain way to make it receive signals from a certain direction.