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Old 29-Oct-2013, 4:24 PM   #1
tomfoolery
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Join Date: Oct 2013
Location: Rochester, NY
Posts: 207
Tivoli Model One strange reception problem with solution

First off, there no longer is a problem, though I don't know why what I did fixed the problem.

I use a Tivoli Model One in my basement shop, a neat little old-school Henry Kloss design that uses a geared analog tuning knob with tuning LED to indicate signal strength and/or station center. Reception was always a problem in the basement, with a folded dipole tacked to the ceiling, wall, both, anywhere that the noise was the lowest on my favorite station near the bottom of the dial. Never no noise - just happy with the least noise.

I put an Antennacraft FM-6 in my garage attic, pointed towards the transmitter at 308 magnetic, ran 100 ft or Radio Shack RG-6 with molded plugs, and got - white noise. Messed about with it, different aiming, different location, nada. Gave up on it and forgot about it.

Fast forward a few years, when I ran across both this site, and an old Phase Linear FM tuner I had from the late 70's, with 5-bar led signal strength indicator and digital tuning, that I had forgotten I still had. Brought it up into the attic, connected with a short length of RG-6, and got 4-1/2 or 5 bars with the stereo light. Brought my Tivoli up there, and got great reception until I hooked up the antenna, then I got - white noise. Lots of other stations, but the one I specifically wanted just gave me noise using the FM-6instead of it's 'internal' antenna.

Brought up still another radio, and got my station clean and crystal clear. Plugged the output of the Phase Linear into the aux input of the other radio, and also clean and clear.

So on a lark (I don't even know why I tried that), I split the signal with a 2-way splitter (-3.5/-3.5 dB), and the Tivoli worked perfectly! No trouble tuning into the station, center light goes brightest at about the center while tweaking the tuning knob, everything works as it should. Back to the basement, and same thing with all of them - noise on the Tivoli, perfect reception on the other two. Use a splitter, with or without resistor on the unused port, and the Tivoli works perfectly!

Now it's connected with a 3-way splitter, with -4/-8/-8 dB taps, and using the -8 at the end of the cheap RG-6 it still works perfectly. The PL tuner shows a little less signal strength on the -4 tap, and maybe a little less still on the -8 (reading between the lines, with the signal strength flickering more or less or not at all, depending on weather and which tap I use), and it all works perfectly even with an additional 100 ft of dual-shield RG-6u, and the 2-way splitter in addition to the 3-way.

200 ft of RG-6, a 2-way splitter, plus a 3-way splitter using the -8 tap, and it still worked perfectly. Direct to the radio, even with 100 ft of RG-6, and white noise.

It's fixed and working, and I'm in the process of making the cable run and 3-way splitter permanent (one to the HT, the other to my basement office), but I haven't a clue as to why cutting in just a 2-way splitter would straighten that one radio right up when it wouldn't work connected directly.

Anyone know why the analog tuned radio wouldn't work on that one station, and the other two digital tuning radio and tuner worked no matter how they were connected to the FM-6? Just curious, is all. It's seems counter intuitive. If the signal was too strong (4 bars), why don't other, stronger, stations cause problems? Why didn't 100 ft of cheap RG-6 (no mesh - just foil) attenuate the signal the way a simple 2-way splitter did, though attenuation alone doesn't seem to be the solution, since even 200 ft of coax made no difference?

I've attached the FM Fool signal analysis in png form, as I didn't see a way to save the report. The target station is 90.1 WGMC, at the beginning of the yellow. 89.7 and 90.5 are about the same strength on the 'meter', but the signal strength doesn't drop much between them as I go up and down .1 MHz at a time, though no 'stereo' light unless it's actually on any of those stations.

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