A question regarding Zenith Trans-Oceanic Radios - UK Vintage Radio Repair and Restoration Discussion Forum

David Pannell · 25th Apr 2013, 4:26 pm

I have a question which I hope one of our members may be able to answer, based on their knowledge of the Zenith Trans-Oceanic 7000 series - or portable radios in general.

I guess this query could apply to many other transportable radios, but in this case, I am referring specifically to two specific Zenith models.

I have a couple of Royal D7000Y, and a couple of R7000-2 radios.

My question is in relation to the use of the telescopic antennas on both types of radio on the FM band:-

The R7000-2 instructions say to extend it fully at 45 degrees for best reception; but the D7000Y instructions say to only extend it by 2 sections at 45 degrees for best reception!!!!! Both radios' antennas are 50 inches when fully extended.

It doesn't make sense to me, unless either the D7000Y has greater RF amplification than the R7000-2, or else they are designed to operate on different fractions of the wavelength!?!?!?

Any ideas

Thanks for your thoughts - and/or knowledge!!

(Don't know if I've suddenly developed a mental block, but I can't get my head round this one at the moment!

Best,

Herald1360 · 25th Apr 2013, 5:57 pm

The only length that would make sense is to extend each telescopic section to about a quarter wavelength for the frequency in use. For 100MHz that would be about 70-75cm for each. Slight variations in length won't make any huge differences.

As for the 45 degree bit, that just gives a reasonable result for both horizontal and vertical polarisation and looks neat. In practice, wave them around for best results on the station you want.

David Pannell · 25th Apr 2013, 7:09 pm

Hi Chris,

I just answered my own question - IDIOT!! Wasn't thinking straight!!

There is part of the antenna inside the radios; thus, when fully extended the TOTAL length is a fraction under 1.5 metres - (1/2 wavelength), and the partly extended alternative, as you say, does equal 0.75 metres - (1/4 wavelength) at 100 MHz, which is a good centre frequency on the FM band (88 - 108 MHz)

Sorry for wasting everyone's time. Brain wouldn't compute earlier!

Cheers and thanks,

25th Apr 2013, 4:26 pm	#1
David Pannell Retired Dormant Member Join Date: Oct 2010 Location: Horsham, West Sussex, UK Posts: 77	A question regarding Zenith Trans-Oceanic Radios I have a question which I hope one of our members may be able to answer, based on their knowledge of the Zenith Trans-Oceanic 7000 series - or portable radios in general. I guess this query could apply to many other transportable radios, but in this case, I am referring specifically to two specific Zenith models. I have a couple of Royal D7000Y, and a couple of R7000-2 radios. My question is in relation to the use of the telescopic antennas on both types of radio on the FM band:- The R7000-2 instructions say to extend it fully at 45 degrees for best reception; but the D7000Y instructions say to only extend it by 2 sections at 45 degrees for best reception!!!!! Both radios' antennas are 50 inches when fully extended. It doesn't make sense to me, unless either the D7000Y has greater RF amplification than the R7000-2, or else they are designed to operate on different fractions of the wavelength!?!?!? Any ideas Thanks for your thoughts - and/or knowledge!! (Don't know if I've suddenly developed a mental block, but I can't get my head round this one at the moment! Best,

25th Apr 2013, 5:57 pm	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: A question regarding Zenith Trans-Oceanic Radios The only length that would make sense is to extend each telescopic section to about a quarter wavelength for the frequency in use. For 100MHz that would be about 70-75cm for each. Slight variations in length won't make any huge differences. As for the 45 degree bit, that just gives a reasonable result for both horizontal and vertical polarisation and looks neat. In practice, wave them around for best results on the station you want. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

25th Apr 2013, 7:09 pm	#3
David Pannell Retired Dormant Member Join Date: Oct 2010 Location: Horsham, West Sussex, UK Posts: 77	Re: A question regarding Zenith Trans-Oceanic Radios Hi Chris, I just answered my own question - IDIOT!! Wasn't thinking straight!! There is part of the antenna inside the radios; thus, when fully extended the TOTAL length is a fraction under 1.5 metres - (1/2 wavelength), and the partly extended alternative, as you say, does equal 0.75 metres - (1/4 wavelength) at 100 MHz, which is a good centre frequency on the FM band (88 - 108 MHz) Sorry for wasting everyone's time. Brain wouldn't compute earlier! Cheers and thanks,