I owned 3 sets of B and C twins, and never thought much of their AM quality. I use an AF67 driving a L4B and get nothing but great audio report's. Like someone else said, look for a Johnson Ranger/AF67-68 or Johnson Viking II. Listen on 3880 KHz Sunday at 8 AM  and judge for your self what the best sounding station are running, it's not that hard to hear what works... Denny 73 K8KAS

Find a nice Kenwood TS50 or a Icom IC706 MKII and a magnet mount and a good Hamstick would do it. I have used Hamsticks for the last 30 years and on 40 meters and up it is hard to outperform them, and they are cheap. IC them at hamfests for $5 and $10
all the time. The TS 50 and IC706 are going for the $300 to $500 range used. Your going to have $400 at least in a package thats worth a darn, for $200 or less just use the cell phone IMHO Denny K8KAS

You have the wrong tube in the amplifier, my Henry 3 K Ultra had a 3cx1200A7 in it and I could get 2000 plus watts out any time. any band with 100 watts drive...

You should check the couplings to the shaft of the var. caps, I once had a loose coupling and could not tune up, as soon as I fixed the loose coupling all was well.

Good Luck it is a nice BIG box once you figure it out....Denny K8KAS

George you need a good RF shack ground, not a 8 foot ground rod but a good RF ground. A number of radials wires 20 or 30 on the ground connected to a plate near the shack and the braid of copper strap into the shack. Most hams now a days don't know what a RF ground is or why your shack Needs one... A lot of these strange problems go away once you have a nice low impedance RF ground..
Running a KW I cannot even get my field strength meter to register in the shack with my ground (50 --  50 foot radials connected to a 12 by 12 inch copper plate and 1 inch copper strap to the rig and tuner..Marconi knew this over 100 years ago guys...Denny K8KAS..

I used this 160 meter antenna at 75 feet high for 6 months and found as others it was OK on 160 and 80, but worthless on 40 meters and above. It tested down 20 plus db from my dipole at 50 feet on 40 meters. I believe the antenna develops many lobes and nulls on bands above 80 meters. It always seemed the station I wanted to work on the higher bands was in a null, the differences on 20 and 17 could not be believed sometimes..Denny K8KAS

Are you NUTS, playing with a radio on a dirt bike, have you ever heard of TREES and HOLES on the trail, you need to pay attention to the path/road/trail when riding a dirt bike, it sounds like a good way to end up DEAD....45 years of trail and road riding under my belt
lets me make this observation...73 Denny K8KAS

Why would anyone screw around with a basic 811 amplifier like this, a pair of vac caps are not cheap for sure and once you made this mod no one would touch it on the used market. Why don't you look for a Quality used amp with a real transmitting tube in it
and parts rated for the application. Nice used Henry for example..73 Denny K8KAS

The problem is simple, your antenna is right over the house, etc. Get the antenna 100 feet or more from the house and your troubles will go away.. The extra 25 feet of coax is nothing, like others mentioned .3 of a db is nothing it would be very hard to measure with Ham type eqpt...I used to run 1500 watts with a 3 element 20 meter beam right over the house and I could light half the lights in the house as well, TV's and radio's were dead meat.. Lots of fun...Denny K8KAS

First 2 meters and the repeater club crap is not Ham radio. Your wasting your time, get on HF and start building or learning something technical so you have a bit of knowledge to chat with. I have been a Ham for over 50 years and if clubs and 2 meters was it I would have been gone in a year, to me they were a bunch of old ladies crabbing about nothing or how to spend the $500 bucks in the club coffers...Denny K8KAS 73

I would be very careful using it on AM, the sweep tube finals work OK on SSB but they with steady carrier will not last. 25 watts steady carrier maybe and no more on AM. AM was not a big thing when this rig was popular. I as well don't remember there even being a AM position on the radio, you can use SSB and offset the carrier balance to get carrier but then have to receive with the BFO on??? It has been a few years but this is what I remember. I would look for an FT101 A-B-E they were good on AM. Drake TR-7 and of course the Drake Twins..The Swan might be asking for trouble. IMHO Denny K8KAS

Can't believe you guys forgot the  Hy-Gain  TH6 and TH7DXX I had two of them and they cooked. The CL33 was a winner as well like others have mentioned. There were 3 or 4 other good antennas in the Toledo area and we often shot it out, the TH6DXX at 75 feet was hard to beat even by a good wide spaced 20 meter mono band-er at the same height...The CL 33 was clean looking and less to handle on the tower than the TH6DXX. The F/B and F/S was much better on the TH6DXX , signal reports were very close...73 Denny K8KAS

I camped and used a 32 foot fiberglass telescopic mast with a wire inside it, this slid over a short 1 and 1/4 in pipe stub on the rear bumper of my camper. I laid 10--30 foot radials on the ground ( I had them soldered together and a battery clamp on one end) I could lay them out in 30 seconds. I fed the antenna with a short run of 300 ohm twin line to the balanced output of my tuner in the camper. I worked 75 meters thru 10 with very good results with this antenna. I liked it over wires/dipole,etc  in that I could keep it out of my next door campers lot (which could and sometimes did cause problems). The antenna was fast and clean and on my lot. It would go up fast and not draw a lot of attention...73 Denny K8KAS

88JK, please, please SWR is not the end of the world, the antenna's efficiency is what mobile antennas are all about. The BIG screwdriver antennas on 75 meter's KILL something like the Hamstick by 10 db or better. I worked at two commercial antenna testing ranges and in my spare time played with Mobil antennas, on 75 meters, 10 db was normal between a Hamstick and my Tarheal 200 with a 6 foot top whip and a small top hat, on 40 meters 3 or 4 db in favor of the Tarheal and on the upper bands 20/17/15 and 10 meters it was a db or so between them. PS, I like Hamsticks BUT there are better antennas for sure.

FYI --10 db on 75 meters is day and night, you can really enjoy 75 meter Mobil with a screwdrive/bugcatcher, etc BIG antenna.

FYI if you have ever been to a Mobil Antenna Shootout you can see the efforts and the antenna knowledge that some of the Ham's have in Mobil antenna's, they are not a bunch of newbies,  for the most part they understand what it takes to make Mobil antenna's perform.. IMHO  73 Denny K8KAS

I used the RG213 on the ground for years with no trouble, but when I put coax a few years ago inside PVC pipe I had water in the PVC and trashed the coax in a year. The pvc was very well sealed at both ends with RTV. The nice thing on the RG213 on the ground it sort of melted into the sand/ground in 6 months and you could not see it. No pipe for me again...Denny K8KAS

What else is on the repeaters any more? I have never heard of 1000's of requests for an audio check and I see no big deal with someone asking for a comment about his/her audio. We have 4 repeaters in the area and nothing really happens anymore on them.  Repeater regs/rules, PL and a total lack of anything technical lost me long ago.   Denny K8KAS