Blyat!

Here's one of my favorite examples.

If you really dig into N6LF's articles on ground radials for vertical antennas, you can come to some astonishing conclusions.

With a small number of radials on the ground (as is not uncommon, especially for temporary/portable operation) using his experimentally-derived shorter lengths versus the traditional free-space-1/4-wave-plus-5% can get you as much as 5.5dB of improvement. That's almost a full S unit or 4 times as much power, just by changing the length of radials, and shortening them at that. Someone will come along and say, well I just use 64 full 1/4 wave elements... which is great, except that only gets you 1.5 to 2dB more signal than 6~8 of the optimized lengths.

my own experiments, although I have only done this with QRP 10 watts so far, is that using a single elevated or not none cut tuned radial and  tuning that radial with a manual antenna  tuner is much more efficient in received signal  and radiated power output than 4 cut tuned elevated radials for portable ops. the added bonus of using the same wire radial for all bands. You can take almost any length of vertical radiator, use an antenna tuner to tune it best you can, then use the counterpoise antenna tuner to get a near perfect SWR and the power out and signal in both go up dramatically

WRT radials and verticals:

The N6LF bit is going to be an interesting study over the next couple of years. At the far east side of my yard I'm planning to erect something that resembles a couple of 5-squares. Hustler BTVs (one unmodified 6BTV and another that covers 11-12-17-30-60) spaced 1/4w apart at 10.125MHz. Each will have satellite 1/4w vertical radiators for the other bands that will be driven via phasing lines - the patterns will be remotely controllable.

Aim here is to put the array in place each fall after I do a final mow of the area then leave it in operation over the relatively QRN-free months (let's say from late October through late March) before storing it for the warmer months. Anchor points for each vertical will be set in concrete, and everything but them (including radials) pulled up prior to growing season.

If I did 64 radials per element, I'd be in hella money for the wire - and getting them all in place would take weeks. Best I can tell from online maps, our soil electrical conductivity is around 15 millimhos - increasing to ~30 the closer one gets to Cleveland. I foresee a lot of interaction with my field-strength meter as I figure out what works best here.

I usually put out 8 of the lengths from his research, from looking at his graphs that seemed to be a good compromise point of return vs cost+difficulty. They seem to work well.

In the FWIW department I managed to WAS and DXCC on the PRC 320 with ease.

30 watts and a random wire.

If I'd bothered to turn in the logs from years ago I'd have WAS on 80, 40 and 20 with the HW-8...DXCC on 20, 15 and 10 with the HW-8/HR-2510.

10M was mobile to/from work with the 2510 and a 1/4w bumper mount whip. The others were park/portable operation with the Heathkit and assorted wire antennas decades before POTA came into being. It was just fun to throw the rig and supplies on my touring bike then go find some place different to operate from.

When I achieved the contacts for WAS on LOTW and learned that my first award from ARRL would cost me almost $50 it was at that moment I decided I could design and print my own award certificate for a lot less

I just keep logs there. I won't be paying them for a certificate.

I look at it and think that if I am getting an S3 report, with an amp I could be getting an S5.

Since this topic is going, during the net tomorrow night, when it's my turn, I'll put the amplifier @ 1.5KW in standby and come down to the driver @ 35 watts.  The actual signal change on the receive side doesn't always change in db like predicted.  Sometimes 35 watts to 1.5KW makes 20db+ difference, sometimes it doesn't even change the receive a single S unit, it all depends on the propagation path.

Folks would have to turn off any preamps and AGC.

A real-world 10M example of this, involving line-of-sight propagation:

One of the locals has an Alpha 9500. He drives it with 35-40w to get full output.

S6 with just the exciter around 50w. He reduces drive a bit, puts the amp inline and is S9 at 1500w indicated.

Another has an 800w output amplifier and will change from S6 to a little under S8 when going from barefoot exciter (100w) to amplifier engaged. No skywave propagation factors into this, so the deltas can be regarded as pretty accurate. And the signal meter calibration regarded as such.

If I want to get really picky I'll put a lab DMM that's accurate to. 0001v across the right  AGC line, make measurements and do a power calculation that way.

I dont need or want any certificates

Crusty Kurt, AKA Kurt N Sterba, did a column for World Radio back in the 80's on the myth of the calibrated "S" meter and at that time stated that an accurate, calibrated "S" meter, as a piece of test gear, would cost more than your HF radio.

Back in those days I found a "N" to BNC adapter in the shop that had a 30 dB loss at some frequency we used in the paging industry. Of course, one of the other techs ran off with it, probably to stick it in somebody's test setup. In the same shop, if somebody put on a radio station that wasn't liked (evening shift) a generator with a piece of wire dangling from it's BNC and tuned to the offending station soon made an appearance. LOL This trick didn't last long once every body caught on. hth
73,
Rob

That's just silly. Measuring RF power is fairly straightforward. A better question might be why do so many radios do this poorly? Grabbing a signal from the AGC is just a dumb, lazy, cheap way of approximating things.

Any competent RF power meter references the power measured to the connector on the front or rear panel. That means it corrects the reading for any attenuation or preamplification in use. This is simple math.

Flex radios and any openHPSDR-compliant radio (HL2, Apache, TRX Duo, Red Pitaya) measure power with good accuracy and linearity. I'm not 100% certain but I believe the same can be said for Elecraft.

The only things subtle about an S-meter compared to a lab RF power meter is that the S-meter standard:

a) Requires that the metering system shall be based on quasi-peak detection with an attack time of 10 ms ± 2 ms and a decay time constant of at least 500 msec.

b) Is almost always implemented as band-limited aka channel power measurement, e.g. if your IF filter is set to 500Hz then the power measured is that which exists in that 500Hz passband.

Where else are you going to get a meaningful approximation of single-signal strength (or aggregate in passband) in an analog superhet?

Why do they do this poorly? Let's think in terms of dynamic range. I'll pick 100dB from no signal to gain saturation as an example, but most contemporary HF rigs are capable of considerably more.

There aren't many meter driver circuits whose range also approximates (let alone closely matches) the receiver's dynamic range due to the characteristics of the small signal devices used in them. And then there's the meter movement itself, which can also exhibit nonlinearity.

Many of you may know Rob Sherwood. I've worked on and off with him on JRC bugaboos over the years. A case in point is the NRD-515 - its S meter nonlinearity at the lower end of the scale is well known in the shortwave community. Best we've collectively been able to do is to get it accurate a little below S5 through full-scale; true 6dB/S-Unit tracking (including scalar increments above S9) is possible with diligent circuit adjustment after incorporation of a couple of his mods. Anything more would require carefully graphing meter deflection per applied current at a number of points across the range then redesigning the driver circuit to take into account such idiosyncrasies. Of course, you'd have to do it for each meter you encountered.

Since Arfhams are at least 20dB/S-9 at all times it's not worth the effort. Y'all are linear or something.

Log amp after the final passband filter. Correct the voltage with scaling amp's that accept preamp, AGC and RF gain voltages and any up front attenuator settings. It's just a bunch of op amps for implementation.

This becomes a small matter of software/firmware in any "modern" IF DSP architecture radio, which is most of the radios on the market these days.

It's not a dynamic range problem if it's done as described above.

As I've posted many times, my pet conspiracy theory is that marketing told engineering at the big three Japanese companies to intentionally make the S-meters non-linear at the low end in order to provide the appearance of a "quiet" receiver. When people move up to Flex, Apache and Elecraft radios they are often shocked to see that their noise levels are truly S5 or worse, not the S2 their I, K or Y radio has been telling them for years.

Not that it matters, but I've worked with Rob as well

Yaesu did similar in their FT-980 - and carried the concept into the ALC circuit. The S meter is VERY linear. ALC...has too much hysteresis, particularly on carrier modes. I've observed this on all four of them I own and many others have as well.


If the total gain of the driver circuit doesn't closely approximate that of the receiver itself at various input levels, you'll still see nonlinearity. I know of a couple commercial-market receivers (used for EMI measurements or similar duties) which lack an S meter altogether. They take an approach akin to yours and present the user with a numeric input power readout which starts at the lowest discernible level that the instrument can hear. Depending on front-end design and power handling capabilities, some of these can directly measure a range from -135dBm to +10 or even +20dBm. But this is meaningless to the average end user, even when he or she has the ability to store and graph deltas during operation of the set. So...the old standby S meter gets the nod.



The true test of receiver noise figure occurs when we disconnect the antenna, turn up the gain all the way then measure the AF output level with a high-precision DMM. It should be at or as close to zero as possible. If noise present, thermal in the IF Amp stages and detector - and possibly the AF Amp section as well. For this you can thank the bean counters. Choose the correct components for the job at hand (keeping the overall noise figure in mind) and it's possible to have a quiet analog receiver. But when price overrules performance...

Speaking of noise:



Two of Rob's problem children now live in my shack. A pair of NRD-535Ds. Loop 1/Loop 2 issues which were a little challenging but turned out to be mechanical. Nevertheless, fixt. Pull the antenna off either, turn the gain all the way up and you'll swear those receivers are dead. But either can easily hear a .01uV signal from my generator. Reconnect the antenna and ohmygarsh...S5 and higher noise on the low bands.

FWIW, an R-71A and an IC-751A and a TS-930S and a TS-830S and every other of the almost 100 rigs on my operating desk or storage shelves will register the same, though some are more intrinsically noisy than others (see above). I haven't put a true SDR or SDR hybrid in the lineup yet but I expect the results to be similar.

It's not meaningless at all. A power meter is a power meter, either more or less accurate and linear depending on how it is implemented. If the user interface is designed to only display in dBm or dBuV then, yeah, it's somewhat obscure for the majority of hams. But fixing this problem is simply a matter of how the information is displayed, not how it is measured.

For instance, take a look at both SmartSDR and Thetis, the two preeminent SDR clients. Both will display an S-meter scale while simultaneously displaying either dBm or dBuV values. And both will work over a range of at least -135 to +10 dBm, accurately and linearly, and all referenced to the rear panel input (i.e. attenuation, preamp gain, etc. are all accounted for). All S-meters should be like that.

Folks in the openHPSDR world have put a very fine point on this. The panadapter in Thetis is almost as good as a lab spectrum analyzer. It shows resolution bandwidth, passband SNR (in S-units or dBm), average noise level in dBm/Hz, and a few other odds and ends. If you calibrate your Thetis-based receiver with a reliable (ideally traceable to NIST) signal generator it is damn good.

I'm not sure where you were going with the noise figure discussion...

That was in regards to your noisy receiver comments.

I can think of a few analog or hybrid models off the top of my head that ARE inherently noisy - even fairly recent production stuff. I can also think of another (very vaunted and collectible) late 70s/early 80s receiver which as delivered from the factory was very quiet - with or without an antenna connected - yet sensitive. But there's this internal adjustment which sets the IF Gain pedestal, and if Joe Screwdriver gets a tuning tool into it then the set begins hissing like a snake. A good number of receivers lack the feature/capability and I'm wondering if this is what makes the YaeKenCom stuff more prone to atmospheric hash. Or appears to.

Sounds like my 245. It's a little weird how quiet it is, I thought it was dead when I first got it.

Contemporary bench in the shack has a couple sets of twins - JST-135/NRD-525 (2ea). Another pair - Raytheon RAY-152 (JST-171, stripped-down -135 built for marine use) and an Edvis PLAM-equipped -525 - used for FT8 and general SWLing duties rounds things out.

All of them are also quiet as a tomb. Like you I was surprised upon connecting the rigs to an antenna. But stations which didn't even light the first bar of the graph-style S meter were and are perfectly readable. This stuff is the best upper HF gear I've used bar none.

FWIW, I own a JRC group on Groups.io. Dan Robinson owns the other one. I suppose we're it in terms of support these days.

We all want more fars.

Not just the fars. Also the rares.