Hi!

You measure RF voltage right across the dummy load, or right across the SO239 coaxial receptacle on the rear panel of the rig.

When making the neutralization adjustment, the final amplifiers should be "shut off" and not producing any power, so ANY kind of 50 ohm load will work fine, it need not be a 100-Watt rated load.  A 51 Ohm 1/2-W carbon resistor soldered across a PL259 is fine.  And the voltage to be measured is directly across that resistor.

73 de Steve WB2WIK/6

The Micronta VOM won't do the job; its test leads are uncontrolled impedance, and if it has an AC Volts range (some VOMs don't even have one), it is undoubtedly neither broadband enough nor sensitive enough to do this job.

A "sensitive RF voltmeter" is one having its RF detector located right in the test probe and providing RF detection sensitivity of <1Vpk at 28 MHz.  VOMs have neither.

However:

If you have a second HF receiver (not the TS520, but a different one), you can use that for this adjustment; or

If you have an oscilloscope good to 50-100 MHz with its normal 10x test probe, you could use that for this adjustment; or

You could homebrew an RF detector (diode, resistor, capacitor) in a little film can or other small suitable housing, to convert RF to DC and then use your existing VOM on a sensitive DC scale (probably 0-1V).

The objective in this particular case is to "drive" the 6146's with the final tubes shut off (not amplifying), and tune the neutralization capacitor for MINIMUM output voltage at the transmitter SO239 coaxial connector.  This essentially "tunes out" the tubes' interelectrode capacitance and neutralizes the tubes.

If you haven't done this before and have no idea what it's about, finding a local ham who is more experienced in this area to help you would be a great idea.  

73 de Steve WB2WIK/6

What did the problem turn out to be?

It's nice to be pleased with the service, but I'd be more disappointed that an IC-746, which cannot be very old, should even need service!  Good grief, my TS850S/AT was born in 1989 and, after being used virtually 7 days a week for the past 12 years, has never required any service...nor has my older Drake TR7A, which dates back to 1977.  It's been used 43,680 hours (combined transmitting/receiving) over 23 years and has never had the cover removed, since I installed an optional filter & noise blanker 23 years ago.

Good service is nice, but what about "service life?"  

WB2WIK/6

That's ridiculous.

Why not simply buy a surplus Variac (voltage variable transformer) and do this, yourself?  You wouldn't need a large one, a 5A unit (or higher current rated) would do just fine.  

Readily available new, but also available less expensively used, from Fair Radio Sales (Lima, OH), http://www.fairradio.com

Just wire it up with a plug and a socket, plug in the equipment, and slowly crank up the voltage from "zero" to "full" over a period of a few minutes.

73 de Steve WB2WIK/6

I've used (for many years) an ordinary Bencher paddle sitting in the center console between the front seats.  In my car, it just happens to fit there perfectly, a snug fit that won't let the paddle slide or move at all, while still providing easy access to the paddles.  Since I'm right-handed, and my right hand just falls naturally into the position to work the paddle, it works out great for me.  If I were left-handed, I'm not sure what I'd do!

I've never had the problem of the radio being too distracting from driving, or vice-versa.  I think it's a matter of having operated CW for so many years without ever writing anything down, anyway (I keep a simple logbook at home, but record nothing in it except date/time/band/station call worked), I'm just very used to operating without paper, pencil or anything else.  I can generally "store up" about ten QSO's in my natural memory bank, so I can log them when I get home, if I wish.  Don't know what would happen if I made 50 QSO's on a trip -- I'd probably forget most all of them.

It's good practice, for mobile operating, whether CW or phone, to just forget about meter readins, output power, SWR, S-meter indications, or much of anything else...these things are distracting.  Just tune around and make contacts!  I often call CQ while operating mobile, and usually get answers.  In fact, I probably get more answers than I can hear, since my receiver sensitivity is limited by outside noise when I'm mobile.  This is a common problem with HF-mobiling, just live with it!

It does help to have a good (but small) communications speaker aimed directly at you, at head-level if possible, as opposed to trying to listen to the top or bottom mounted speaker of a mobile HF rig, that is likely mounted under the dashboard somewhere.  I use a Radio Shack amplified communications speaker, which requires both an audio line and a +12Vdc connection, but it sounds GREAT and can be driven by almost any wimpy, low-volume source.  That speaker's mounted on top of the dashboard, to my left so as not to block the view of the road, and aims right at me -- it's very loud and crisp, and makes working mobile a pleasure.

73 & happy mobiling!

Steve WB2WIK/6

There is a benefit to using a good balun: It should be 1:1, as a center-fed 1/2-wave dipole has a feedpoint impedance nearly 50 Ohms.  By properly transforming your unbalanced feedline (coax) to your balanced antenna (dipole), the feedline is much less likely to radiate or receive undesirable noise, much of which is vertically polarized and will be nulled to some extent by the horizontal polarity of the dipole.

The MFJ antenna tuner will be superfluous with a resonant 40 meter dipole.  Unless you intend to use the 40m dipole on other bands where it's not resonant, you won't need the tuner.  The 40m dipole should work fine on its third harmonic, 15 meters, without a tuner also.  It will not work well on 20m, whether you use a tuner or not.

73 de Steve WB2WIK/6

Hmmm.  What kind of G5RV is that?

The normal G5RV design uses twinlead for about 33' and then coaxial cable (to the rig) after that, so there'd be no reason to have ladder line connecting to your rig.

However, the G5RV is also non-resonant and does not provide a reasonable impedance match on all bands; in fact, the only band where its impedance is nearly 50 ohms is 20 meters.  On all other bands, the G5RV normally requires a broad-range antenna tuner, and the limited tuning range of the "internal automatic" tuners in modern HF rigs is normally insufficient.

73 de Steve WB2WIK/6

The right way to do this would be to replace the bandswitch and add an input tuning network tuned to 18.1 MHz, as well as an additional tap point on the 10-15-20m pi-net coil, specifically for 17m.  This falls into the range of "can be done," but it's quite a lot of work and may or may not be within your capability, depending upon how experienced you are with amplifier construction.

A much easier way, that will not provide nearly as good results but ought to work to some extent, is to simply re-tune the 15m input coil for 17m, and use the 15m band position on the bandswith, tuning for 17m.  Whether the pi-net will actually "dip" at 18.1 MHz is questionable, this is a pretty far stretch for the circuit, which normally tunes 21 MHz.  But it's certainly worth a try, and should only take a few minutes to prove one way or the other.

I did a complete WARC band conversion to an SB220 several years ago, by replacing the bandswitch with a 7-position switch and adding separate tuned inputs for 12m and 17m, as well as new tap points on the 10-15-20m pi-net inductor, to make it all properly resonant on the new bands.  It worked fine, but was quite a lot of work and the new switch cost more than $100 as a surplus unit from Fair Radio Sales (Lima, OH).

73 & good luck!

Steve WB2WIK/6
 

Charles, it's difficult to be objective in head-to-head comparisons of equipment that has so much varied functionality.  Unlike a drag race or a 1/4-mile foot sprint, where someone is clearly the winner and the others are clearly losers, equipment evaluation tends to be very subjective and even more so when the equipment is placed side by side.

I wrote dozens of equipment reviews for the ham mags over the years, mostly for CQ Magazine back in the 1980's when I was a contributing editor (1984-1988), and the conclusions were almost always highly subjective, e.g.,

"The Icom has an MDS that is 3dB better than the Kenwood; however, that sensitivity is not usable with an antenna connected to the receiver, because atmospheric noise limited sensitivity to -129 dBm on the least noisy band, even with a small connected antenna.  As such, that 3dB added sensitivity in a closed system is wasted, and probably explains why the Kenwood, with less measured sensitivity, actually sounds more sensitive when connected.  With the Kenwood's better shaped audio response, signals producing more AGC activity in the Icom actually sounded stronger on the Kenwood..." (blah, blah, blah)

It's that kind of thing.  Which is why even the best, most technical Product Reviews which utilized well trained and experienced technicians using a million dollars worth of laboratory equipment are not quite as valid as a "test drive," actually using the gear to see how it feels.

I do see this occuring in automotive magazines, too...like Road & Track, Car & Driver, etc.  It is fairly common for the car that has the flat-out best acceleration, skidpad handling and other attributes can actually "lose" the side-by-side contest, based on "feel" for the driver.  Kind of like: The Corvette is a much higher performance car in every measurable aspect, but my old MG-B is more fun to drive!

73 de Steve WB2WIK/6

I think you mean "clear" LED, rather than "white."

I've done this in old rigs like the IC720A, using ultrabright LASER type LEDs, which are at least as bright as the original grain-of-wheat lamp being replaced, and obviously last a lot longer.

I've used HP series HLPM ultrabright LEDs, but Nichia makes something similar.  Wire a 220 Ohm, 2W resistor in series with the LED anode lead, and connect to the +12Vdc wire originally used to power the lamp.  The other LED lead (cathode) goes to ground, or the wire originally used to connect to the ground-side of the lamp.  If it's not obvious which wire is + and which is ground, use a VOM to find out!

73 de Steve WB2WIK/6

The "coil of coax" cannot create a 4:1 balun.  It's just an RF-choke type balun which helps isolate the transmission line from the antenna by choking off RF current flowing on the outer surface of the coaxial cable's outer (braid) conductor.  It provides no impedance transformation.

To make an impedance-transforming balun, one can certainly be constructed of coaxial cable, but the intended transformation will occur only at one frequency, because this is a tuned transformer (tuned by the coaxial cable length).  As such, a coaxial 4:1 balun, which can be constructed of 1/2-wavelength (in coax, using the Vf formula) connected as a phase shifting network between the balanced sides of the antenna (and not as a coil in the transmission line), is normally used for monoband yagis and such, and not for any antenna intended for multiple band operation.

A 4:1 "wideband" balun is most easily constructed of wire windings on a heavy-duty ferrite toroid core.  If you haven't made one before, great information is in the ARRL Antenna Book; Walt Maxwell's (W2DU) book on Baluns and Ununs; and other texts.  However, commercially made and readily available wideband, high-power 4:1 baluns for HF operation are also a good choice: They don't cost much and are normally weather-sealed and convenient to use.

I've used the Radioworks 4:1 baluns <http://www.radioworks.com>, type B4-2K, with great success.

Of course another option with an EDZ is to just bring the open-wire or ladder line directly into your antenna tuner, eliminating the need for a balun or coax altogether!

73 de Steve WB2WIK/6

This is not an ideal situation, at all.  The slinky is sharply resonant on its fundamental (1/2-wave) frequency, and even more sharply resonant on its harmonics.  Even with 450 Ohm feed and a good tuner, I'd think it would eventually drive anyone nuts trying to actually use it on multiple bands.

If you have access to your roof (which you must, if you were thinking about laying a slinky on it!) and 450 Ohm ladder line, I'd opt for a single wire loop, stapled around the circumference of the roof.  This can be stapled under the eaves to hide it, and becomes quite invisible if insulated wire of the same color as the eaves are painted is used.  Make it a complete 360 degree loop, with just a small space (opening in the loop) where the ladder line attaches.  It needn't be resonant, although if you can make it resonant on your lowest-frequency band (e.g., 80m loop would be 253 feet overall length -- this requires a pretty big house, so maybe shoot for a 40m loop, which is 131 feet overall: A rather small house has this circumference) it will work better there, and won't be nearly as sharply resonant.

This kind of loop works even better "above" the roof, supported just above the roofing using screw-in insulators so it's not actually touching the roofing.  I've noted 5-6-7 dB improvement in exactly the same HF loop, supported an inch or two above the roof as opposed to laying directly on it.  That's a lot to pick up, if you can.  But a good tuner will tune it, either way.

Good luck!

Steve WB2WIK/6

I seriously doubt that the VHF vertical and A3S will have any interaction at all -- there's no possible reason for them to.  As for the 40m "L" that is two feet lower, that's not much to go on.  Why an L?  Do you really mean an inverted vee?  An L is usually horizontal at the feedpoint (near the ground) and then runs vertical to its end; it's also not a very good antenna, which is why most are installed as an "inverted L," where the antenna runs vertical at the feedpoint (near the ground), ties off to a high point, and then runs horizontal to its end.  In this manner, it behaves much like a top-loaded vertical and is quite an effective antenna.

In any case, whatever it is, if you install the "L" top support as a piece of rope over a pulley mounted on the slip-up mast below the A3S, you can raise and lower the 40m wire antenna from the ground and note if it has any effect or interaction with the triband beam.  When installing wire antennas of any type, I always use at least one pulley in the system to facilitate easy raising and lowering, as wire antennas always require some field-tuning to get them resonant, and it's a big pain to raise and lower multiple times without using pulleys.

Re the station-to-station interference: My solution for this in Field Day is to run QRP, battery power.  At 5W there's a whole lot less interference between stations (typically "none"), and without generator noise you can really hear weak signals (and also avoid headache from the constant drone), each contact is worth 5x the points of a "high power" contact, and battery power provides bonus points.  While QRO yields masses of contacts, the highest powered stations rarely "win" Field Day...if the objective is to have a fun, peaceful weekend that produces the maximum actual score, QRP is the way to go!  And of course, make more contacts on CW than on phone...they're worth an additional 2x multiplier; e.g., a single SSB QRO contact is worth one point, while a QRP CW QSO is worth TEN points.  It's easy to see why the highest scoring FD stations use this strategy.

73 de Steve WB2WIK/6

This is not specific advice relating to the IC2100H, but in general, many mobile rigs will do this (lock up on transmit) if the power supply voltage is too low.

In fact, it happens all the time when mobile operators are transmitting and then shut off their engines...the voltage to the rig drops about two volts, and the rig locks up on transmit.  The solution is to shut the rig off, or start the car again!

So, just in case this is the problem: Check your power supply voltage.  These rigs are designed to operate at 13.8Vdc +/- 0.6Vdc (13.2 to 14.4V), below 13.2V a lot of them misbehave and do weird things.

73!

Steve WB2WIK/6

I've modified several HF amplifiers to work on six meters, and very successfully; however after modeling the AL811 and AL811H using computer tools it appears these are not candidates for such modification.

Reason: The 811A tubes, which were not designed for VHF use, have very high Cgk (capacitance from grid to cathode) which will make tuning the input to 50 MHz extremely difficult, especially with three or four tubes in parallel.  They also have a pretty high plate capacitance, which, again, when used with 3-4 tubes in parallel will make the Q of any conventional plate tank circuit too high to be very usable at any substantial power level.

After modeling, I estimate I could get a single 811A to work on 50 MHz, but 3-4 in parallel presents too many obstacles.

Amplifiers more suited to conversion are those using VHF tubes, e.g., the NCL2000 which uses 8122's, or any amplifier using 8874's or an 8877; or amplifiers using a single, large tube (rather than paralleled tubes) to create substantial power, such as the 3-500Z.  The Ameritron AL80B, with its single 3-500Z, might be pressed into service on 50 MHz if all input/output tuning components were removed, along with the bandswitch, and replaced with a pi-network Q=4 for six meters (plate tank) and a toroid transformer for the input network.  Its filament RF chokes would also need to be rewound for less inductance, to prevent self-resonance on 50 MHz.  But it seems very do-able.

I most recently converted an old NCL2000 to six meters, successfully, for W6YLZ.  That amp was a great conversion candidate because it uses two 8122 tubes, which are rated for full power operation to 400 MHz!  The 811A's cutoff frequency is only 60 MHz.

73 de Steve WB2WIK/6