"Does price buy performance or satisfaction in an HF transceiver?" - now on YouTube

Karl is correct on hiss (this is a great pun, I will leave it) his analysis, but there is a 'coupling coefficient' that needs to be mentioned.

Today's receivers are so sensitive that the SKY NOISE dominates the noise component of the sensitivity. With few exceptions, most hams overall will seldom encounter cases where the RX sensitivity is a limiting factor in a modern HF transceiver. The sky is louder than the receiver noise, to put it simply.

You can show this yourself for YOUR system as simply as listening to the RX, and attaching and removing the antenna cable from the SO 239..if this background hiss is perceived louder with antenna on, then the RX outperforms the limit set by the sky noise.

If you have a modest setup that sky noise is a constant and moderate limiter to the sensitivity of the SYSTEM. However, if you have a high gain antenna, especially at great height, or a low noise loop or Beverage, for example, the angular steradians sampled and or local noise rejected by the antenna may cut down the overall sky noise and the limiting sensitivity is set by the RX in the transceiver.

IOW 'weak signal' work needs better antennas than a G5RV up 30 feet, for example.

One of Karl's points is that if you have a great transceiver it is somewhat wasted without a great antenna. This is one of many examples why.

 

To close this thread out from my participation, I want to thank those who made constructive comments and thoughts. No empirical study is perfect, as I made clear remarks in my invited talk to the Cycle 25 Hub to where I thought limitations were in this one.

It’s clear though that the subjective elements of an HF rig purchase seem to outweigh price and measured Rx performance per se. What my results show is that price (and performance) has a much smaller relationship to Rx performance and COLLECTIVE satisfaction as exemplified in average eHam ratings than much rhetoric among individual hams would suggest. But this is exactly why we do such research: to find out such answers.

Thanks for the ideas! I’m pursuing the addition of Tx bench measures as well as examining the statistical relationship of price and measured performance on the INDIVIDUAL eHam ratings. I’m also using a natural language processing of the actual text in those ratings to measure various themes and sentiments about each rig. Those results are about a year away, I’d guess.

If you’re interested, you can learn much more about how Rob Sherwood and Bob Allison (ARRL Lab) goes about their bench measurements and why in my feature interviews on the ICQ Podcast, Episodes 305 and 312, respectively. But you will have to take the time to actually listen, lol!

 

"It has become a common practice in recruitment activities to show youngsters "DX-chasing" or contesting from well-equipped stations in low- noise locations.

The contrast to what they are going to experience when building their own station with a 1oo W radio and a G5RV at 5 m height with an ambient noise level of S9 is striking."

That. Right. There.

The Drivers' Ed car is a Bugatti, and the kids first car is a 98 Ford Escort.

Disappointment, followed by departure from the ham radio hobby.

When you're stuck in a noisy location with a crappy antenna, numbers no longer matter. In this case, an Icom 718 is just as effective as a Icom 7851 - although the latter is a way larger and prettier paperweight on a desk.

Performance is determined by price.

Satisfaction is determined by your antennas and location.

 

Having made measurements of the noise performance of both civilian and military HF receive sites since the early 1990s, some observations can be made.

It is very seldom that the antenna noise figures, which are determined by the antenna size and the ambient noise, are under 20 dB, even at the higher HF bands. At the lower, values of around 30 or 40 dB are common.

This makes system sensitivity quite independent of the receiver noise floor as long as the antennas are large enough. Small antennas pick up a proportionally lower amount of ambient noise.

If there are no local noise sources, the antenna noise figure is substantially constant with azimuth for directional antennas.

On the lower HF bands, it becomes quite difficult to build antennas large enough that they may discriminate against any directional dependency of noise levels.

From the reports I have authored over the years, there may be some trends identified. Even receive sites "in the outbacks" are somewhat affected by power-line noise and sky-wave propagated wide-band interference, presumably from LED lighting and switching power supplies.

To reduce the influence from electrical appliances altogether, it takes extreme measures. Fully suppressing an obnoxious interference component in a military installation required powering off a fire and burglar alarm in a building located almost a kilometre away from the antennas.

The number and severity of man-made interference/noise sources have increased considerably over 25 years, and they have become much harder to locate, as they are so plentiful.

An amateur, living in a semi-rural or suburban environment, who is using full-size antennas may expect an antenna noise figure today in the order of 35-40 dB on bands below 10 MHz, and 20-35 dB above.

A typical modern rHF eceiver has an SSB noise floor without the attenuator or pre-amp activated in the region of -125 dBm, corresponding to a noise figure of 15 dB. This noise floor is well below the noise received from the antenna, except when the antenna is very small electrically.

Tuned loops are representative for such antennas, and of course active antennas.

In situations where the noise or IMD sidebands of transmitters are the limiting factors, the receiver noise floor becomes even less insignficant.

73/
Karl-Arne
SM0AOM

 

SEE: Post #76, and----

Exactly.

Thus using a TRANSCEIVER 'performance to price' metric has no meaning in real world situations.

It's the SYSTEM 'performance to price' metric that has relevance.

Thus the main point of this presentation is flawed in its conclusion.

Welcome to the 'inner circle' Karl. I will teach you the 'secret handshake;-)'

 

IMO, its not subjective at all, and people are a lot smarter than herd animals.

People know what their full SYSTEM setup is capable of , and spend the least money they need to match that with the transceiver that goes with it. Folks don't go out and buy IC-7851's if they have a G5RV up 30 feet. You don't buy a super sensitive (RX) transceiver when your noise is mostly coming from the sky, not the RX.

People buy FEATURES and seldom buy specifically for PERFORMANCE.

Hams buy LOTS of transceivers--and sell them! They OFTEN do this because the REST of the station has improved and thus a better transceiver is justified in that mix. Just look at how many HF transceivers--LESS THAN A YEAR OLD-- are for same on HAMSWAP. I see 4 on the main page as we speak.

 

Isn't this what systems engineering is all about?
To find the best and the most economical compromise between many, sometimes conflicting, requirements.

Regarding the "inner circle" I was taught the basics about receiver systems integration and characterisation already in the early 70s by two of my mentors,

SM4:s COK

and AWC.


73/
Karl-Arne
SM0AOM

 

"On the shoulders of giants..."

 

Pff! They don't do it only because they don't have money ...

 

Perhaps not the IC-7851, but the IC-781 some 3o years ago.

According to the then Icom sales rep in Sweden, more than one
came back and complained bitterly about their difficulties working DX, despite having bought a very expensive radio...
73/
Karl-Arne
SM0AOM

 

Yes, I was fortunate to meet qualified people early in my career.
Both SM4:s were prolific writers, and in 1970 I was intrigued by a journal
article written by SM4AWC about systems dimensioning.
It contained two graphs, one of typical field strengths as a function of distance at the FOT:

the other typical noise field strengths


It is interesting to see that the expected noise field strengths of "yesteryear" were some 10-20 dB lower than today, and that receiver sensitivity was of very secondary importance on HF already then.

For me, who previously had compared receivers using the sensitivity specs and had built low-noise preamps and preselectors also for the "DC bands" it was an eye-opener.

SM4COK was a senior engineer at Ericsson and VHF/UHF enthusiast, and became primarily responsible for making me taking "the narrow path".

He explained very patiently why a low noise figure was important on VHF, the more the frequency increased, and even more when the antenna was pointed to the sky. Also, he taught me to dimension using "system noise temperature" which makes a lot of things much more easy.

In the mid 80s, in connection with my first ITU assignment, I was fortunate to getting to know a very experienced specialist about noise, both man-made and natural, dr. Thomas Damboldt, DJ5DT(SK).

His material about the seasonal variations of MF and HF atmospheric noise, and the guidance in interpreting the CCIR 322 "Radio Noise Atlas" was a very important input for the determination of coast station coverage areas in the GMDSS, for which I became responsible of in Sweden.

As usual, "you learn as long as you live".

73/
Karl-Arne
SM0AOM

 

If I had $13,000 to buy a 7851, I wouldn't. Instead, I'd buy a tower, some yagi antennas from GXP and the required accoutrements.

I'd go bigger outside, not inside.

 

Old saying:

"One $ in the antenna, equals at least $3 in the radio..."
73/
Karl-Arne
SM0AOM

 

May be the future of RF receivers.

New quantum receiver the first to detect entire radio frequency spectrum
https://phys.org/news/2021-02-quantum-entire-radio-frequency-spectrum.html

One atomic sensing element achieves unprecedented bandwidth, spanning MHz to THz, and dynamic range extending below 1mV/m to 10kV/m and above.
https://www.rydbergtechnologies.com...ve atoms in small vapor-cell sensing elements.

 

Once again: THE SYSTEM TEMPERATURE IS DOMINATED by SKY NOISE . This is true from MF all the way up to SEVERAL HUNDRED MHz. The Rydberg demodulation system has no benefit if it has no way to lower the SKY NOISE--which it doesn't.

Karl-- Why don't people GET this?