Alignment Advice.

[Joe]

That was why I made it in the first place. It will also be handy for aligning live chassis sets where a direct connection cannot be made safely.

- Joe

[Skywave]

Thanks Joe - that's what I suspected - but I thought I'd just check first.

I can understand your thinking: the ferrite rod isn't fully effective on account of the break in it, so use the external loop to get a bit more signal from distant transmitters into the radio. But depending on how you couple that loop to the radio, doing that is likely to mess up the alignment of the 'front-end' R.F. tuned circuits - and that may well explain some of the results you have obtained. The first R.F tuned cct. is expecting to 'see' just the right amount of inductance and capacitance as the set is tuned over its frequency range. By introducing the loop, that inductance has now changed (the amount of change largely dependent on the degree of coupling from the loop to the set), so consequently, the 'front-end' tracking will be thrown out of alignment, and that mis-alignment will be frequency-sensitive, of course.
The most effective remedy, of course, is simply to replace the broken ferrite rod.

As for sets that do not use a ferrite rod, but with an 'internal aerial', that aerial will still comprise a critical-value inductance for the first tuned cct. in the set, so the above comment is still applicable.
For valve sets that are designed for the traditional 'longwire' running down the garden, then yes, I can see that a loop (of almost any dimensions) will be beneficial to some degree, if the traditional '100-foot longwire' is not available.

HTH,
Al. / March 13, 2013 //

[Skywave]

Pity - most audio gear I use has 600 ohms as an option, but defaults to low-Z. In audio terms, 600 ohms went out with the dinosaurs.

Really? When I was employed by Eddystone Broadcast, (up to a few years ago), the vast majority of audio equipment that we supplied to the BBC World Service had 600-Ω interfaces. And quite a lot of other customers around the world were similarly supplied with 600-Ω audio systems too, albeit sometimes with 75-Ω as an additional option.

Al. / March 13th., 2013 //

[Mark Hennessy]

Yes, but the Word Service was using really old gear - what would have been considered "legacy" even at the time. Local radio still uses similar stuff in some parts of the country. But anything made post 1980 will be hi-Zin, low-Zout by default, perhaps with options for 600 ohms if they want to sell to people with legacy installations.

Bear in mind I'm talking general studio and broadcast centre kit. It's different in transmitter installations, which are always much longer-lived - and don't get changed operationally like studios.

But take it from me - 600 ohms is a PITA. I don't miss it

[pwdrive]

Yes, but the Word Service was using really old gear - what would have been considered "legacy" even at the time. Local radio still uses similar stuff in some parts of the country. But anything made post 1980 will be hi-Zin, low-Zout by default, perhaps with options for 600 ohms if they want to sell to people with legacy installations.

Bear in mind I'm talking general studio and broadcast centre kit. It's different in transmitter installations, which are always much longer-lived - and don't get changed operationally like studios.

But take it from me - 600 ohms is a PITA. I don't miss it

I was in the transmitter room at Redruth main transmitter at Four Lanes, back in the mid eighties, the Radio Cornwall stuff was all modern, some stuff was labled Home, Light and Third... The transmitter manager had rigged some emergency cooling for something or other which kept breaking down, it consisted of a standard plastic cold water tank, a ball cock and some bits of copper plumbing! the overun of the main tv transmitter transmission line up to the antennas was coiled under the floor to maintain the matching impedences. Had a chance to climb the mast with him but I declined..

Lawrence.

[boiss]

Before trying to align the set I would get hold of a new ferrite rod, any sort of botch job on a previously badly repaired rod may result in tracking problems and reduced sensitivity.
Mike

[Joe]

As I said in Post 46, the set now has a 'New' ferrite rod and seems to be fine.

- Joe

[boiss]

As I said in Post 46, the set now has a 'New' ferrite rod and seems to be fine.

- Joe

Whoops, I'd forgotten when it it got picked up by someone else.
Mike