[EdHolland]

Hi Folks,

Thought I would ask here. I am putting together some information for another publication, The Lowdown which is the journal of the Long Wave Club of America. There has been discussion of low noise antennas, the history of which traces back to the 1930s and the emergence of short wave receivers. Interested by this I have been trawling American Radio History, and patent sites to glean more about the beginnings of the technique. This quickly brought up a Philco angle, in the form of the "All Wave" and "High Efficiency" antennas.

If anyone here knows more about these, and when they were marketed, I would be very interested to learn more. They seem to fit the low noise/anti interference description, having coupling transformers at the antenna and receiver, and a balanced shielded twin line feeder. I nearly bought one on ebay a couple of weeks ago, but it went for more than I was willing to pay for such a collectors item.

30's publications show references to several similar systems by Kolster Brandes, CorWiCo, Belling and Lee (UK) and a few others. To me it is an interesting, and still relevant subject - modern or antique receivers can still benefit from very similar configurations.


Thanks in advance,

Ed

[Chas]

Fact is: That antenna to be most efficient must be resonant. That does not work well for a general coverage receiver. A resonant antenna will have a specific impedance at the feed point that is or can be made to match common feed line. Matched to a feedline that line is resistant to interference. A matching device at the receiver for the line impedance must also be broadband...

There are commercial receiver antennas that will do this. The issue would be matching at the receiver.

The overall antenna as a system will be noise free all along the feedline but not at the antenna. Noise can still enter there.

FWIR RCA used a design called the spider web antenna. A delta matched dipole that was feed by 72 ohm twisted pair. One such model did not need the heavy center balun (heavy as it was in a porcelain housing). The "normal feed impedance of a dipole is 72 ohm, the feed line can be a pair of 14-18 ga. stranded, insulated wire twisted 1 turn in two inches.

Some 30's - 40's era radios included provision for the balanced antenna. Ready for such a feedline. The Delta system has several extended legs that assist in managing the shortwave bands. For BC overall, the antenna serves as loading and the feedline does some reception if one leg is connected to ground.

IMHO the use of baluns for BC will introduce loss and unexpected resonances. I think a more than adequate BC/shortwave antenna is an easy afternoon project costing only for the wire & insulators.

Do not neglect the lightning protection, can be homemade.

YMMV

Chas

[Jake Blake]

". . . the feed line can be a pair of 14-18 ga. stranded, insulated wire twisted 1 turn in two inches."

I think this topic could (and should) easily occupy a category of it's own.  I have about 100 questions about it.  

[EdHolland]

Chas,

Thanks for the detail. I know in general about antennas, and the efficiency that comes through resonance. Receive is a bit more forgiving than transmitting, but the principles still hold of course.

I found one article that IIRC showed how one of the designs (not Philco I believe) flattened out the response curve.

The other articles I found indicate that the intention was that the antenna could be placed outside, and the balanced lead-in could approach the house without picking up the near field interference from domestic wiring etc. like a simple long-wire would have done. The designs also helped prevent the radio from conveying wiring noise out to the antenna.

This is indeed something that could be a thread all its own, because the isolation methods using transformers do still work brilliantly, especially in keeping the antenna and house wiring separate.

Cheers

Ed

[Ron Ramirez]

Do not neglect the lightning protection, can be homemade.

I would like to hear more about this. Never heard of homemade lightning protection before. I'm currently using a lightning arrestor intended for an electric fence. If there is a better way, I'd like to know...

[EdHolland]

Ron - I've seen a few implementations while reading through the 1930's

One is to use an automotive spark plug, grounding the body, and connecting the antenna wire to the center electrode. The gap can be narrowed (a lot) although I have not seen this mentioned.

Another is to use a Neon bulb - they act quickly and have a striking voltage ~ 70 V. One of my newer receivers, made by Icom, has just such a feature, soldered directly to the antenna socket just inside the radio's chassis.

Still another is to use two stacks of fast recovery diodes, wired in opposite polarity across antenna and earth. Two or more are usual, allowing for higher real signal voltages before the diodes themselves cause spurious signals through intermodulation. Lots of modern comms receivers use this approach.

Quick google images search on the subject


P.S. Anything on All-Wave or High Efficiency Antennas?

Cheers,

Ed

[klondike98]

Here are some threads discussing all wave and HE antennas
https://philcoradio.com/phorum/showthrea...t=all-wave

The link is no longer active but the wayback archive has it:
https://web.archive.org/web/200603281526...0-6112.htm

[EdHolland]

Thank you Bob

[Steve Davis]

I would like to hear more about this. Never heard of homemade lightning protection before.

A sparkplug can be used as a lightning arrestor.


Steve