In the USA more than one linear amplifier manufacturer used a Millen HV connector, which offers virtally no protection at all, as an external HV lead with voltages over 2000 volts. I personally knew two people killed by such connectors. In both cases they reached around back of the amplifier to do something or they were trying to move something and grabbed the HV lead.

People need to get over worrying about other people.

I call CQ DX any time when I am looking for foreign contacts. It is virtually always productive, and tells stateside people I am looking for quick longer distance contacts. The last thing I want to do in the common DX areas of any band is work across town when the band is open for 10,000 miles.

As a matter of fact, it is wasteful to work 1000 miles on prime frequencies that are populated and usable for much longer distances.

As for just waiting for DX, that depends on if the DX is transmitting and can be found. As a general rule the stronger station should initiate a random frequency random calling long distance QSO. It is different for skeds or planned operation, but for randomly initiated contacts it is far more effective for the higher ERP station to start the ball rolling.

In the 1960's, when power was limited on 160 meters and antennas and equipment were generally poor,  USA stations called CQ DX on the even first parts of 5 minute periods, and DX called on the start of odd 5 minute periods. That was standard operating. It was agreed to world wide by anyone wanting to work across the ocean to NA.

Somehow someone gave people authority to disparage and dictate what great Lids people are when they qualify where or who they really want to work, and somehow we gave authority to people to say operating habits that are actually pretty reasonable and effective are not good because someone finds they don't work for them, or they personally just don't like the method.

Many larger stations have been the first DX contact for 100's of smaller stations on 160 meters, and it is because of CQ's followed by careful listening for DX signals down in the noise. It is almost impossible to do it the other way, and find a noise floor signal that is calling CQ for their first ever DX contact.

I'm sure this applies for other bands, too.

73 Tom

Chris,

Some late comments:

First about eHam reviews. Don't put so much stock in what they say. They are a combination of emotions and feelings more than something exclusively technically accurate. The more prone something is to operator error the less favorable the review. The worse the general reputation of a company the more accepted a bad review is. If you look you can find things that don't work at all but come from a favorable place that get reviews like "it did not work at all and I put it in the closet, but it is a 4 out of 5".

Back to the topic. Signals and noise are so strong on lower frequencies, like the AM BCB, that 20 uV is far more than enough level. You might worry about 1-2 uV on ten meters in a quiet location, but not on low bands. The exception would be with a terrible antenna.

The single largest issue you will have is impedance mismatch between the receiver and the antenna source. You are cutting up a receiver, or thinking about cutting up a receiver, when some very simple outside changes are all that are necessary.

If you pull the antenna off and hear a large background noise drop between busy channels, you have all the sensitivity or antenna matching you need for that antenna.

If you do not have that happen, you should probably look at simple external ways to improve antenna match to the receiver before worrying about removing the attenuator.

My largest problem around the house with my old BCB radios is noise around the house from all the SMPS and other things making noise now. I have to pick antennas for reduced noise from devices around the house, rather than sensitivity.

73 Tom

That's the same reason I like old rigs. I like to work on them and learn what the designer did right and what the designer did wrong.

What I found is many just copy what others did before, and must not have much thought about the circuit and why things are the way they are.

One common thing are voltage dividers in keyed RF stages that depend on the tubes loading a series resistance to the supply. When the key is up the voltages soar to high levels, and that makes open key voltages go through the ceiling. It also makes some very funny waveforms.

You'd be surprised how some minor changes make a large difference in performance. My EF Johnson rigs, for example, have floating plate tune capacitors. They have a small buss wire to the sockets for grounding. This is derrived from when things were on wooden chassis, and carried over through habit to rigs built on metal chassis. The poor grounding of the tank tune capacitor results in poor harmonic suppression, and a capacitor shaft very hot with RF. It actually makes the Ranger and Valiant jump frequency or chirp on some bands, as RF gets from the shaft through the front panel and into the VFO capacitor shaft!

It's very interesting to look at the old rigs, and find and fix real issues. We don't have to gut them and put in super hi-fi mods (that often cause other problems) to make what problems they had go away.

http://www.w8ji.com/johnson_vfo_chirp_jump.htm

73 Tom

The clue right away when something is going to be followed with nonsense is when someone says, "this shows the xxxx does not follow the same rules as other antennas".

Dan,

He had more than impedance mismatch issues going on. A small loop is so lossy that it is someone immune to external loading. The antenna, in effect, has its own parallel dummy load inside.

I've been through exactly the same effects he had with small receiving loops. In 1970 or so I got the brilliant idea of nulling local noise by tilting my small mag loop horizontal. It went dead, even though SWR did not change. (It was so lossy, earth had little effect on impedance.) Tilt it vertical, and the signal came right back.

The problem is pretty simple. The earth shorts the electric field. That's why it reflects horizontally polarized signals so well, even poor dirt. When the electric field is taken to near zero in an electromagnetic wave so is the magnetic field, the EM radiation is attenuated.

It's a pretty basic simple thing.

Even if we took a dipole and made it very low near a reflecting surface, the signal would be attenuated. That's why NVIS antennas need to be some reasonable height to have reasonable efficiency, and why loops "go deader" when laid horizontal close to a reflective plane. Since saltwater is a virtual short, he killed the fields.

All antennas work on the same rules, and none are special or magical. The minute someone claims something behaves differently and is immune to rules, get your waders on! The bull droppings are about to get deep.

73 Tom

The 5/8th wave or 1/2 wave verticals obtain their gain because the current area in the antenna is elevated higher above the groundplance. Without a flat groundplane extending out some distance a 5/8th wave has no gain, it can even have loss.

Put a 5/8th wave low on a vehicle so only the upper part clears the sheet metal, and pretty much every advantage goes away. You might as well just use a 1/4 wave on the roof as a 5/8th on a fender.

The earlier in the audio chain you sample the audio, the more stages you check for linearity and response. You have to be careful to not go too early, because the audio bandwidth might be too wide in early stages. That can make it appear impossible to get 100% modulation at some frequencies without going over on others, because of the frequency response slope.


An L pad is almost always better, but a low impedance load can almost always drive a high impedance load without any issues.

If not, what AC5UP suggested will work.

 

Why not just talk, or are you working on some problem?

73 Tom

That sounds good. The plate does not need to be thick. Whatever mechanically will not be too flimsy will also be thick enough electrically.

I use 18 ga hard copper. That's .040 thick sheet. 

Let's think about his demonstration on the beach, and if the loop has "unique properties compared to other antennas", like he claims:

1.) He lays the vertical loop flat, so it becomes a horizontally polarized antenna just barely over saltwater, and it goes dead.

Anyone here surprised? You shouldn't be! Lay a dipole in the sand over saltwater and see how it is. Lay any vertical on the beach flat, and see how it works.

2.) He raises the vertically polarized loop up above his saltwater ground, and he doesn't see much change.

Anyone here surprised that a vertical works pretty good at low height over saltwater??

3.) He places a larger loop near a smaller loop, and the signal gets better with a certain critical spacing (and tuning probably).

Anyone here surprised that a larger antenna coupled to a smaller antenna makes the efficiency increase?

73 Tom

There are some unusual common ideas about ground rods.

First, one rod per leg.  Let's suume that is correct. If I have a 50 foot tall pipe support, it only needs one rod. If I have a six legged mast the same height, it needs six rods.  Does this make sense to anyone?

Second, lightning and rod depth. Does anyone think a rod or group of rods is a better path for lightning than a bunch of cables to the house that connect to everything in the house and the utilities? I can't imagine a rod, or even two or three rods, is worth much. What really helps protect against lightning is how the cables are routed and how they enter the house. That is probably 90 percent or more of any protection issue.

While I'm not disagreeing towers should have some ground rods (I almost always use four copper pipes), ground rods really are a very small part of safety. As a matter of fact, without proper entrance bonding and with a short mast or tower near the house, a ground rod might make things worse.

I would install at least a few ground rods spread some distance over trying to get an extra few feet of depth, but more important than anything, I would do a proper building entrance that follows national codes. That's where the bulk of safety is gained.

(My ground rods mostly support a buss wire that I attach multiple buried radials to. The buried radials do the bulk of lightning and RF grounding.)

73 Tom

I would look at simple things first, instead of just wildly leaping to some major problem.

Zero grid current or low grid current with low output and high plate current is a clear sign of too much load coupling. This might not be the problem, but every Ham in the world who has run a GG amplifier should understand these symptoms because it is a critical basic in how any GG amplifier should be tuned.

I can easily make an 8877 tube go near zero grid simply by running the load control too far open (not enough capacitance).   When I mistune an amplifier this way, plate current is too high and grid current is too low. Output power is too low, and the amplifier becomes very peak emission sensitive because peak cathode current sky rockets.

You might have a different problem, but before disecting the amplifier or changing tubes I would see how the amp behave with more loading capacitance.

By the way, the real symptoms of a bad tube are:

1.) Slightly to moderately high input SWR and low output, with lower than normal plate and grid currents, indicates low emission

2.) Negative grid current and high pplate current, with very high input SWR and no output, indicates a grid cathode short.

Excessive plate current and no or low grid current almost NEVER indicates a bad tube.

I took some advice on forums and put an old telegraph key in the dishwasher, and it totally ruined it. It removed the glaze from the Bakelite. I also have had problems with printing or dials with something as simple as Windex.

After a few cases or trouble, I just just use warm soapy water unless I am SURE what I use causes no problems. For tubes, I use air and 100% pure alcohol, xylene, or acetone.

Think of the scope as a comparison between two things. It compares the audio input to the RF output between two sample points you choose. It tells you the linearity difference between those two chosen points.

If you sample at the end of the audio, like at the modulator output, and then at the PA output for RF, you only check the PA stage modulation linearity. If you checked at an earlier audio point to the output of the RF section, you would check the modulator high power stages and the transmitter for linearity.

The audio tap point ideally should be before any stages that add distortion. You get a better picture of real distortion when you sample an earlier audio stage, if the scope has enough sensitivity.

If I wanted high reliability and good performance I would stay away from Hex and Quad antennas totally. I would either buy interlaced element Yagi antennas, or good trap antennas. I have Force 12 interlaced antennas and in about 15 years only had trouble with one ten meter antenna element. The tip cracked and broke off from vibration. After that happened I put rope in the element ends and they stopped rattling in light breezes.

15 years is a long time without maintainence!

I'm not sure about trap antennas, but the Yagis are exactly the same. As far as I know MFJ made no changes at all to any of the antennas. I have five HyGain 205CA antennas, five HG 155CA, and six 105CA antennas and they are identical to the ones I bought in the 1980's. The only problem I had with the antennas was the slitting of a 20 meter element section was missed, but that turned out to be a documentation error in the original instructions. I don't like hose clamps much, but the Hygain antennas I bought in 1980 had hose clamps. :-) Personally, I would prefer a through-element machine  screw or a different style clamp.

My Force 12's used rivets, which I like even less, but still seem to work on smaller antennas. On a 80/40 antenna the rivets all wallowed out and came loose.

73 Tom

I was involved in modernizing the BN-86 about 15 years ago. It is a current balun.


I'm a little confused by that. Do an SWR sweep if you can and post the lowest SWR frequency.

Maybe your antenna elements are too long.