Already talked with the folks at Alpha with little help, so I'm trying here. Does anyone have a 160M tankcoil (the wound toroid) from an old Alpha PA70 or PA70V they want to sell? Also, would anyone
A buddy of mine has a QRO 2500DX (runs the pair of x800s). Has worked fine for last 10 years. And in the last month, the toroid that serves the 40/80/160m tank has started to get extreemly hot. At on
I don't understand that. Surely at least one end is tied to a tap point! Let's assume the thing has 20 turns and the 20 MHz tap point is at 4 turns. If the 4 turn tap was selected withouit shorting
Years ago I tore apart a small RCA AVT-112 (I am guessing at the numbers). It was an aircraft transmitter for WW-II Piper Cubs types using a 6V6 final on 3 MHz. It had a wonderful inductor tuned by a
Do you think that #12 enameled close wound would withstand the voltage turn to turn? The coil I have is #14 on a ceramic core. The wire is spaced about the same size as the #14. So there is space for
yes I took that into consideration for the calculations. Have you guys taken into consideration that the tank circuit in these amps only transform down to 200 ohms, not 50 ohms from the plate impedan
Hi John, With the Q of 7 to 8 you probably mean the pi network Q. That is not the Q of the particular coil but that of the circuit, calculated by tube Ra/Xc of anode capacitor. Higher Q will produce
<I recommend an open coil type. Especially on 40 and 80. I tried toroids <in my 8877 amp and had the 160 meter unit overheat and start to smoke <when on 10 meters! <Yes, the 160 meter Pi toroid over
That form is grooved too tight for larger wire but Carl also has #10 and 12 heavy enameled copper wire. -- Original Message -- From: "Jim W7RY" <w7ry@centurytel.net> To: <"Undisclosed-Recipient:;"@mx
Have you guys taken into consideration that the tank circuit in these amps only transform down to 200 ohms, not 50 ohms from the plate impedance? After the tank circuit it passes through a 4 to 1 ba
Hi Chuck, I visited your website today and had a look on you project. So far a nice job as your first amp! Connect the padder cap to the 80m switch position only, then it will be in circuit when you
So here is the real fix! I removed the 80 and 160 meter toroids all together. Installed a 2" dia X 3.5" long ceramic coil with 42 turns of #14 wire and hooked it to the end of the 40 meter coil. The
Thanks Peter. I calculate a Q of 7 to 8 for the stock design mentioned in the previous email. There are still a fair number of these amps in use, I wondered if others had similar experience. I consid
ORIGINAL MESSAGE: ** REPLY SEPARATOR ** I second Peter's comments, with an additional observation. I have a Command HF-2500 legal limit amp which uses a toroid in the 40/80/160 meter portion of the t
It is probably a bad idea. The turns in a spaced turn air cored inductor are only loosely coupled, so shorting out turns just detours flux around those turns. Since flux is fringing all over the plac
I know it is common and accepted practice to short out the turns on an air-core plate tankcoil for bandswitching, but is it ok for powdered iron core toroids in that situation? My understanding is t
Jim, Self resonance in a coil is generally from the middle of the coil to surroundings, or from a middle area to the ends. It is NOT across the whole winding. That would be a harmless parallel resona
I used stacks of T225-2 for a mobile antenna loading coil on 40m. Measured Q was around 400. Toroid coils with taps, which no good idea anyway, will have much lower Q. As part of a pi network for 160
Offering for sale to the amplifier builder: A. 10-160m Tankcoil component package complete w/all coils, toroid,and bandswitch wafer. Ready to drop in. $45 B. Panel mount 1P7T porcelain hvy duty band
As I see it, the load is in series with the L - so the current is exactly equal. . The question was about conductor size. . - Rich..., 805.386.3734, www.vcnet.com/measures. end -- FAQ on WWW: http:/