Bad suggestion. That would cause low current, or cause no output, or cause backwards grid current with no drive.



Bad suggestion. That would cause the plate meter to pin against the stop really hard, even at idle.


That causes low output, and some really weird things.

You probably have an older amplifier before the bias system was added. Check to see if there is a string of diodes at the bottom of the board on the rear panel, b down at the bottom near the filament choke.

My bet is you have an amplifier that is older and does not have the bias diodes added. Newer tubes have higher idle current than the first tubes had, and will idle around 180 mA without drive when keyed.

I wouldn't worry about anything at this point. It doesn't sound like a problem.




 

A few constructive comments:

1.) If the crossing vertical boards inside are intended to be shields, they won't be. They have a grossly flawed ground connection. They will leak nearly as bad as not being there at all. To be a shield, it has to be "grounded" at all sides and edges. It looks like you only have a ground lug at the bottom on one wall. To be an effective shield it has to be grounded vertically along the sides, horizontally across the bottom, and even at the top.   

2.) Leads appear to be very long if you expect accuracy at 30 MHz or higher.

3.) If you connect this thing without the ports terminated, you are destined to have high SWR. This is because you have added impedance from the current transformers. Current transformers are only current transformers when properly designed, constructed, and properly terminated.

4.) The sample cable length appears terribly long. Remember although that looks like coax to us, it is not coax to a radio signal. It is a single conductor with a "Faraday" shield, it is NOT in coaxial mode. This means it does not have 50 ohms impedance. (If it did have normal shield function, it would not work as a sample line.)

I really think you have too much lead length everywhere, a poor box, and the wrong cores. When I do an HF directional coupler, I try to limit the current sample length to less than one inch.  At about two-three inches there will be significant standing wave, and it will also affect upper HF null and coupling attenuation to the sample detector.

I'm not sure you need an internal shield wall, but if you do, the shield wall you have now would need grounded at the top, base, and ends. They would need bonded at the crossing point. With crossed shielding, that would be at least 5 grounds and a seam bond at the center.

73 Tom

There is significant inaccurate advice here. It is common advice, but is not accurate. The advice to use a whole house suppressor can help minor surges from distant strikes or other power system problems, but is actually LESS likely to result in good local lightning protection (which is more likely to damage something).

The way it actually works is:

1.) Lightning does NOT need to be shunted to ground to protect something.

2.) Suppressors at the equipment can be VERY effective, and are significantly more likely to be effective than a whole house suppressor.

The goal of a suppressor, be it for RFI or lightning, is to have all cables or conductors entering a zone to enter at the same potential.  To be most effective the protected zone has to be small, or it has to be a closed zone.

It is nearly impossible to enclose an entire HOUSE, although a halo ground (perimeter ground) helps.

It is generally very easy and effective to enclose or group specific equipment clusters, such as a TV/DVR/ stereo center.

Most lightning damage is from common mode currents, not differential voltages between wires in a bundle.

My house had a silly whole-house suppressor on my mains when I moved in. What that suppressor did was limit DIFFERENTIAL surges to a certain voltage.  I was told this was installed because of well pump failures. They said they still had well pump failures.  :-)

This makes sense, since lightning striking a power line would follow the wires in common mode into the house, and clamping them differential mode wouldn't do a single thing for that. It would still follow the wires to or from the well.

The power company service man, when he came to change my drop, asked if I just wanted the whole house thing removed. Even the power company's own employee said the whole house suppressor didn't do much.

If you want to protect things, everything entering the house should enter at ONE point or be bonded to one point. Things off by themselves, like a TV set, should have a LOCAL protector at the device that ties the antenna cable to the mains wiring.

They make outlet strips that do this. Outlet strips that connect phone, CATV, and power mains to a common connection through surge suppressors are readily available, and they are probably hundreds of times more effective than some suppressor thing at the mains entrance. They also do NOT require a ground (more often than not a local independent ground at a device actually makes things worse).

73 Tom

Has anyone looked at these horsefence antennas for loss???

They are manufactured from horse fence tape, with has a ribbon woven with several strands of #26 stainless steel wire.  While they should be brordbanded, they also should have pretty high loss (making bandwidth wide).

There should be a lot of "maybes" with that antenna.

On lower bands, like 80 or 40 meters, a 68 ft long 16 ft wide loop is more like a folded dipole than a loop. This is because wire spacing is 1/8th wave or less. Even on 20 meters the width spacing is just 1/4 wave. This is why feeding in the the middle of a long side works so much better.

Like any 80 meter 1/2 size folded dipole, it will not work well.
It should be OK on 40 and higher, but probably not so good on 30.

I'd keep it away from a metal roof.

R127 is only in the circuit while the relay RL101 is not closed. As soon as RL101 closes, the resistor is shorted. If RL101 does not close, it is very evident. R127 will smoke.

R127 or F101 can fail on start up, with bad tubes or a bad transformer.

What is the history of the amp? Has the transformer been replaced?

The only advantages or disadvantages of different wires are in strength and life. 



Any post insulator is strong. The long tall "poor insulators" I pictured have a strong tendency to break if something pulls on the wire. I had constant failures with them whenever small branches would fall on the antennas.

Tractor Supply and other places have black or yellow stubby plastic post insulators. Others will work, but the nail-through-center, smaller length, post knob insulators are much more reliable over time. 


A slight bend or meander has no effect.

The stubs act like they have infinite SWR, so they have to be very low loss or they will dissipate significant power. Coax will  also have significant common mode currents, and that will ruin pattern. Use air insulated parallel conductor line.


Measure the wire by formula and it will be close enough. Feed a sample piece as a dipole and trim it to length, and that would also work.

The stubs are measured using DTF mode.



I'm not sure what that means.


All you have is three half waves in-phase.  The gain will be about 4 dBd. Capture area will be just a little over  twice that of a regular dipole, provided it has about 4 dB gain over a dipole.

Any antenna you installed that had 4 dB gain on the same band would have the same effective aperture, or capture area. A two element Yagi would actually have a bit more capture area.

Personally, if it were me, I'd build a collinear array with two dipoles fed with coax spaced 1/4 wave apart at the center,  or I'd build a broadside array with two parallel coax fed dipoles spaced 5/8th wave apart. I'd lay a reflector screen below the dipoles.

Those are two much easier ways to do the same thing, and would have much more usable bandwidth.

I understand they really think extra highly of each other to call each other "first class" compared to the rest of the peons in the hobby, but that seems a little over-affectionate for my crowd.

OK. Those pictures sure fooled me. The picture of the transformer really looks like chips, and the relay armature looks skewed!!!

 What band are you on when it smells, and what does it smell like, if it is any smell you recognize?

Did you look close for something that looks hot? Maybe unplug it and sniff around to see what area smells?

Does the HV stay up within normal range when you tune??

 

It is cured now, thanks Mike.'

test

No,  that doesn't work.

The problem is eHam thinks you made a post somewhere within the last 120 seconds. Even if it is a different post, doesn't matter.  It stops your entirely new post.

Then, when you wait on the back window, and try to repost after 2 minutes, it says "you already made a post and this is a duplicate". This happens even if I make a whole new post in the clicked "back" window.

A shorter timer might work, because that would stop the initial freeze.

It looks like Mike sees the issue and has changed something.

 

Marc,

Read my previous post before you do or try anything else.

Tom