Radio antenna selector switch mystery signal boost - Printable Version
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Radio antenna selector switch mystery signal boost (/showthread.php?tid=18999)
+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Radio antenna selector switch mystery signal boost (/showthread.php?tid=18999)
Radio antenna selector switch mystery signal boost - jcassity - 09-23-2018
i have been playing around with the antenna off and on lately.
I brought all my radios to a six position rotary switch to simplify which radio is using my single long wire antenna.
prior to this mod, i had a single 120v relay on each radio that when powered up , the dry contacts of the radio would "connect itself" to the long wire antenna.
I am trying something new so the relays are not in the game right now.
I am not having a problem, i am just posting to say that something odd is happening SPECIFICALLY with the GE Clock radio model 513F.
This set has an internal loop antenna and i tried like heck to integrate it to the long wire for better reception.
I can not in any way integrate the long wire to this GE set from what i have tested.
I did over double the reception of the GE set by simply bonding a short 3' long wire off one side of the loop antenna letting it dangle in free air.
all my radios sit on a common shelf in the garage. The philco lives in the house.
to my mystery issue .............
My GE sits on the shelf with its buddies... i noticed something odd though,
The GE ******ONLY EXPERIENCES A HUGE SIGNAL BOOST*** when the rotary switch is on position 2!!
help me understand whats going on???????
if you all like i can do a short video demonstration.
i drew up a diagram below to show you the one line of how the sets are tied to the outside long wire.
notice the GE is not connected to the long wire.
My only assumption on the source of the signal boost the GE set gets is that the #2 radio made in 1992 might be allowing antenna coupling of some sorts. Again, the ge radio only gets a boost in signal if i have this small 3' long wire hanin' off the back **and** the rotary switch is on position 2. The 1992 magnavox set is powered off as well as all the other sets.
thoughts?
RE: Radio antenna selector switch mystery signal boost - Chas - 09-23-2018
For each of the sets that have a ground connection, use a common ground, each radio with its own wire, not daisy-chained. This ground must be short, direct to earth. Do not use an electrical ground at an outlet...
For the G-E find a way to put two or three turns of wire on the back of the radio as a loop. Or make a small frame of 1/4" MDF make five slots or more odd number of slots and wind at least two turns, weave around the slots. More turns if there is not enough coupling. Mount the MDF in a 2 x 3" block 8" long so it can be slipped out to add/remove turns. Connect the "loop" outside to antenna (6) and the inner to the ground like the other sets. This loop can magnetically couple to any AC/DC radio including a transistor set. Spacing away will reduce coupling. Since there is no electrical connection to the chassis it is safe.
There may be a noise issue with a set that has direct coupling of the chassis to the AC outlet ground. This will create a ground loop if a common ground is used. Even if an isolating capacitor is used it will not isolate noise from the home AC system... You may have to float the AC grounded radio with a ground adapter used without connecting its tab. Then ground the chassis via the "master" ground.
The Hallicrafters may also have a line coupling problem that may be solved by flipping the AC plug, that works unless it to has been creatively modified with the AC switch or/and or an additional safety cap installed. It too, even with AC cord putting neutral on the chassis can couple the AC via the internal bypass cap to the antenna. Resulting in an antenna that will give a tingle if contacted.
FWIK only some vintage boatanchors used a three wire cord. So the above won't apply unless the radio has been creatively modified
Consider a two pole antenna/ground switch if it can have a short ground connections.
Keep in mind the whole exercise is about getting an RF signal to each radio circuit such that the RF flows through the radio or coupling loop from antenna to ground and back. Negating all home AC as an RF ground system...
YMMV be SAFE!
Chas
RE: Radio antenna selector switch mystery signal boost - jcassity - 09-23-2018
non of my sets are 3 prong.
all sets excluding #2 and #4 have a new polarized cord correctly connected / wired.
Set 1 , the exterior chassis is isolated from the exterior chassis.
Set 3,, there is a metal exterior case, pull out the interior skeleton by the two handles and you extract the skeleton and chassis.
on this set 3, the exterior case and interior skeleton are normally bolted together but isolated form the electronics chassis by wood factory blocks,
all my sets do not have a dedicated ground rod.
on the GE, i experimented 7 different ways to sunday. i even removed the loop, kept the ground end on the set and connected the other end to my outdoor long wire,,, its result was nothing but a bunch of humming.
btw,, this GE radio is dead tonight,, dono why but i wondered why i looked over at the clock and time was kinda setting still, its cause the clock want running, nor will the radio power up so... i bust into it sometime tomorrow
im gonna have to read your post a couple more times, you said a lot and i want to soak up the ideas your handing over.
thanks
Scott
RE: Radio antenna selector switch mystery signal boost - Chas - 09-24-2018
Scott,
Quote:...all my sets do not have a dedicated ground rod.
...on the GE, i experimented 7 different ways to Sunday. I even removed the loop, kept the ground end on the set and connected the other end to my outdoor long wire,,, its result was nothing but a bunch of humming.
An external antenna must be considered a "complete circuit". RF intercepted and returning to Earth. and vice-versa, flowing back and forth at "all frequencies". The current antenna cannot develop this "flow" except via stray or deliberate coupling via internal coupling capacitors within certain radios.
I can only assume the G-E is in a poor reception area as its internal loop is in play. Some of my text asks for the creation of an external loop for the G-E. The purpose of which is to couple the "greater strength" of the external antenna to the G-E's internal loop. There must be that Earth ground to "close the circuit" for the external loop to be excited with RF.
It is this same RF flow via the antenna and Earth (ground) that must be established for each of the sets taking account of how the RF is "flowing" in the respective antenna input circuit of each radio.
Some radios couple ground to establish the Earth antenna current flow via the AC line. That works but must be considered when an external Earth connection is made. Returning RF to Earth via the home electrical system often introduces noise and in some instance becomes a significant part of the antenna system generally with poor results. Modern home electronic equipment will use switching power supplies as well as discharge lighting, etc.
Noise from home electrical equipment is often not recognized as a primary contributor of poor receiver sensitivity. The noise creates an AVC signal just as effective at reducing the gain of the receiver as much as the desired programming.
A majority of noise enters the radio via the antenna, but also via the power cord, especially when the radios design uses the power cord as the RF return.
Once a suitable SHORT ground to Earth is installed then work from there discovering the best method to couple the radios antenna to the switch.
As for the sudden failure of the G-E. If the power cord has not been recently replaced, check where the cord exits the molded power plug. When the radio was in service, the power plug may have used in an outlet where during the "daily" room cleaning the cord was moved back & forth. That motion will eventually breakdown the strands of the wire causing an intermittent...
GL
Chas
RE: Radio antenna selector switch mystery signal boost - jcassity - 09-24-2018
got it, i understand everything your saying.
-on the GE set,, relocate a newly fabricated and calibrateable design loop antenna outside so it can couple with my long wire.
**this must mean i need to omit the original loop antenna, save it back.,,, or do you mean parallel in another?
--The GE is back up now, i was tinkering / experimenting on the minerva set cause i cant seem to leave well enough alone. I unplugged the 6' long 20position power strip i have dedicated to the garage sets and simply forgot to plug the strip back in. I was trying to isolate out where this minor 30 or so volts ac was coming from on the skeleton frame that holds the isolated chassis. Also i was tinkering around with an idea i had about a simple S meter for the minerva.
-provide a ref ground rod.
**i have had a dedicated ground rod since i started learning this tech a couple years ago. the 10' 3/4'' copper clad stainless rod while tied to my philco, the hallicrafters s38, the minerva, not a single radio acted any different with or without the ground rod connected. since the ground rod is near my garage, i went ahead and cad welded the sol #2 tinned and built a wall penetration/fire stopping caulk. since all my work adding a ground rod added no benefit to any of the 7 sets i have brought back to life since joining here, i went ahead and bonded the new gndrod to my garage sub panel instead as a contingency plan b to harden my ref ground out to the garage. my garage panel board has separate N and G bars so this rod aint separatly derived so dont worry on that too much. the garage now see's 12ohms.
A member here was helpin me out with a problem and ground rod condition came up so i acted accordingly to address it. Even if all my work proved to be useless or useful, attending to the probable fault was worth the time. at least at that time we knew the grounding was not my problem. weather i liked it or not, the probable fault needed to be confirmed or eliminated.
--the philco does infact have a 3 prong cord,,, yes i get what you said about using the 3rd prong as the sets ref ground with respect to reception performance, its impossible in my honest opinion to use UT ground as an RF ground,, its just too darn dirty in my opinion only.
--in all my years living here, i have not found my UT service entrance ground rod, and im betting since its build was 1976, prior to NEC, i bet i would be finding corroded friction connections or acorn taps which are not good. inside my panel board i read with my AEMC ground tester that i have 87ohms,,, not bad but ,,, i bet it could be much lower like commercial applications where i try to target less than 15ohms even if we have to drill a water well & drop in sol #2 with a cad welded rod. Now you got me thinking about a counter poise ground system, i have plenty of welded wire i could lay out flat below grade,, maybe just a 4'x8' sheet of it would do. A guy i know from this generation of tube radios told me that if i have a ground rod properly in and noise remains, trench a horizontal to the left and right of your rod then lay another rod in the 24'' or so ditch then bond the two together. lay out some salt mix then back fill & compact. he said that when he was at raytheon, they did this on some of the arrays in dam neck va navel base and it helped cancel out unwanted noises to about 40% additional when a megger was used in re-commissioning the grounding.
RE: Radio antenna selector switch mystery signal boost - jcassity - 09-24-2018
so back to the original question.........
i have a decent signal on the GE with it sitting on the shelf and the signal over doubles when i rotate the selector switch to position 2.
why is this again? coupling with radio set #2?
i just thought of sumthin' , i can answer this real quick like,, i will move radio 2 over to rotary position #6.
i will turn on the GE and have the rotary switch on position 1.
i should expect the GE to have a decent signal.
if rotate the antenna selector switch to position 6, i should double my GE reception.
this will prob answer my question i guess
RE: Radio antenna selector switch mystery signal boost - Chas - 09-24-2018
Quote:Scott: on the GE set,, relocate a newly fabricated and calibrateable design loop antenna outside so it can couple with my long wire.The G-E radio stands unmodified. Calibrated? No way just a few turns of wire as big an area as the loop built into the back of the radio. Even if there is a ferrite loopstick. The new coil and the existing loop in the radio will creat an RF transformer with no electrical connection to the radio. For this loop transformer to work it must have the short, direct ground to Earth.
**this must mean i need to omit the original loop antenna, save it back.,,, or do you mean parallel in another?
Quote:--The GE is back up now, i was tinkering / experimenting on the minerva set cause i cant seem to leave well enough alone. I unplugged the 6' long 20position power strip i have dedicated to the garage sets and simply forgot to plug the strip back in. I was trying to isolate out where this minor 30 or so volts ac was coming from on the skeleton frame that holds the isolated chassis. Also i was tinkering around with an idea i had about a simple S meter for the minerva.The"30 volts AC" is leakage, it can be coming from any radio that has line bypass capacitors or a transformer powered radio with a leaking primary winding. As long as it is less than a few ma it is a non-issue.
The AVC can be monitored with a battery powered DVM on a low voltage scale or the IF or RF plate current monitored. Both schemes will show relative changes in signal level. An accurate "S" meter is a defined circuit that is directly related to the sensitivity of the receiver, generally reference 600 ohms.. I have never modified a receiver for an "S" meter although I have radios with "S" meters OEM...
GL