22-07-2020, 09:50 AM
(This post was last modified: 22-07-2020, 09:54 AM by Mike Watterson.)
Works on all bands (though higher SW bands needed a DK96 swap) on the "new" tag by inspection for the 33K HT feed to the LO primary coils. RTE1 at times quite loud, there is an intermittent connection somewhere.
The aerial wire to whip, rather than being only on SW bands, is connected also in some fashion on MW & LW. Add too much wire and the rod aerial reception is swamped by local noise on LW. Though right now at 10 am there are only stations on LW. There might be something on the 40m to 20m SW band, but likely needs a better SW set. It does pick up the signal generator even at 20MHz, just pick up via the aerial wire, no coil or connection, just the unconnected test lead on generator radiating.
The detector IF coil, secondary of IFT2, is just a bit lower in Q, as you'd expect from solid wire rather than the approximately 4 to 6 strand enamel Litz. AFAIK the only reason for fabric covered wire is to reduce the self capacitance on large LW & MW windings by increasing turn/layer spacing. It's also the reason for wave winding. Lots of "modern" ferrite rod coils are actually single core enamel wire with a fabric covering.
The primary is about 5 Ω and my new secondary is slightly thinner wire than can be used, my next size up or my fabric Litz would only fit about 100 to 150 turns rather than 240 approximately. L is proportional to N squared, due to mutual inductance, which is why two identical inductors give 1/2 in parallel and x2 in series, if not coupling. If they are unshielded and very close, then series will give near zero or x4 depending on polarity and parallel doesn't affect L, but doubles Q due to halving the resistance. RF flows only on the "skin", thinner at higher frequencies, hence hollow pipes or steel core works at VHF and higher. So Litz increases the Q for the same amount of copper due to skin effect. It's multiple coils in parallel.
There is something intermittent on gain. Perhaps a valve socket, bad joint or intermittent switch contact. I had it working on batteries for the first time. A B101 using four stacks of CR2032 paralleled via 1N4148s and wire fuses and 2 x Alkaline D cells in the LT holders. Up till now I've been using 63V from 2x bench PSUs in series with current limit set (both have reverse diodes on outputs and other protection) and using the LT on a 90V/1.5 B126 sized battery eliminator, which gives about 1.42 quickly dropping to about 1.32V on no load as the pair of series shunt rectifiers across the o/p warm up.
I always use that sort of LT or D cells as that clamps any accidents with HT.
Also I disconnect HT when changing parts on battery sets as many only switch HT- and either LT+ or LT-. It's best anyway on anything to disconnect supply and not rely on on/off switches.
The aerial wire to whip, rather than being only on SW bands, is connected also in some fashion on MW & LW. Add too much wire and the rod aerial reception is swamped by local noise on LW. Though right now at 10 am there are only stations on LW. There might be something on the 40m to 20m SW band, but likely needs a better SW set. It does pick up the signal generator even at 20MHz, just pick up via the aerial wire, no coil or connection, just the unconnected test lead on generator radiating.
The detector IF coil, secondary of IFT2, is just a bit lower in Q, as you'd expect from solid wire rather than the approximately 4 to 6 strand enamel Litz. AFAIK the only reason for fabric covered wire is to reduce the self capacitance on large LW & MW windings by increasing turn/layer spacing. It's also the reason for wave winding. Lots of "modern" ferrite rod coils are actually single core enamel wire with a fabric covering.
The primary is about 5 Ω and my new secondary is slightly thinner wire than can be used, my next size up or my fabric Litz would only fit about 100 to 150 turns rather than 240 approximately. L is proportional to N squared, due to mutual inductance, which is why two identical inductors give 1/2 in parallel and x2 in series, if not coupling. If they are unshielded and very close, then series will give near zero or x4 depending on polarity and parallel doesn't affect L, but doubles Q due to halving the resistance. RF flows only on the "skin", thinner at higher frequencies, hence hollow pipes or steel core works at VHF and higher. So Litz increases the Q for the same amount of copper due to skin effect. It's multiple coils in parallel.
There is something intermittent on gain. Perhaps a valve socket, bad joint or intermittent switch contact. I had it working on batteries for the first time. A B101 using four stacks of CR2032 paralleled via 1N4148s and wire fuses and 2 x Alkaline D cells in the LT holders. Up till now I've been using 63V from 2x bench PSUs in series with current limit set (both have reverse diodes on outputs and other protection) and using the LT on a 90V/1.5 B126 sized battery eliminator, which gives about 1.42 quickly dropping to about 1.32V on no load as the pair of series shunt rectifiers across the o/p warm up.
I always use that sort of LT or D cells as that clamps any accidents with HT.
Also I disconnect HT when changing parts on battery sets as many only switch HT- and either LT+ or LT-. It's best anyway on anything to disconnect supply and not rely on on/off switches.
