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Philco 38-10 Antenna input - Printable Version

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Philco 38-10 Antenna input - Guest - 04-07-2008

While restoring my 38-10,I noticed in my Riders that that when using the factory supplied "All Wave Antenna" (basically a dipole) one side of the antenna is always at chassis ground potential regardless of band switch position (The black lead) .IMHO,this renders half of the antenna useless for reception.Is this a factory goofup or is there a reason for this? 73 de Bill

- exray - 04-07-2008

W4NJF,

It apparently is just like a half-wave ham dipole. The 'active' side is a quarter-wave. The other side is basically serving as a counterpoise.

This arrangement allows for resonance and a low impedance feedpoint. Look at the SO-239 on the back of your ham gear. Its at ground. Icon_smile

Some sets do this arrangement using a balanced feedline and/or balun/xfmr. Not sure if one is any better than the other in this application (broadband).

- Guest - 04-08-2008

hI EXRAY,Gotta disagree with you on this one,in the 1937 Philco models that used the same antenna,the primary antenna windings were center tapped to ground and the antenna itself was switched to "T" configuration on the BCB and operated as half wave dipole on SW.The exact resonant frequency of the antenna was dependent on how long you cut each leg-usually about 12 Mhz (25 meters).So why put a dipole for 40 meters in length when one for 20 would do?(for rx purposes only!).I can see your take on the counterpoise,but I'm not talking verticals here.

- Chuck Schwark - 04-08-2008

The bandswitch does the balaned/un-bal switching, I believe.

Chuck

- exray - 04-08-2008

Bill Fulling Wrote:hI EXRAY,Gotta disagree with you on this one,in the 1937 Philco models that used the same antenna,the primary antenna windings were center tapped to ground and the antenna itself was switched to "T" configuration on the BCB and operated as half wave dipole on SW.The exact resonant frequency of the antenna was dependent on how long you cut each leg-usually about 12 Mhz (25 meters).So why put a dipole for 40 meters in length when one for 20 would do?(for rx purposes only!).I can see your take on the counterpoise,but I'm not talking verticals here.

If its a question of length then they were possibly operating the dipole at both 1/2-wave and 3/2-wave lengths. Using a freq 12 Mhz (25 m) just for example...a dipole of 37.5 meters in length will work as well if not a tad better than one of a 12.5 m length PLUS the 37.5 m one has the advantage of working at 4 MHz (75 m wavelength) as well.

I have no idea if thats what they had in mind but a dipole would work that way.

-Bill