"Among radio amateurs, it's worth asking whether the laboratory measurements provided by ARRL, Sherwood, Adam Farson, or Peter Hard - RadCom are truly meaningful criteria for selecting a transceiver."
How to Choose a Radio for Your Location — A Slightly Different Approach
Introduction
Not long ago, I started thinking about upgrading some of my radio equipment. My trusty HF transceiver, FT 920 which had served me well for many years as a backup rig, was slowly making its way toward retirement. Although the radio itself still met all my basic needs, its protocol and software support were clearly outdated.
These days, the market is flooded with high-end amateur transceivers, with price tags reaching astronomical levels. Their technical specs are indeed impressive, at least according to Sherwood and ARRL test results. One of the latest examples is the Yaesu FT-101D MP, which boasts some stunning figures:
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MDS = –136 dBm (Minimum Discernible Signal, or sensitivity)
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BDR = 150 dB (Blocking Dynamic Range at 100 kHz spacing)
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RMDR = 120 dB (Reciprocal Mixing Dynamic Range, reflecting phase noise performance)
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IMD3 @ 2 kHz = 110 dB (Third-order intermodulation products at 2 kHz spacing)
But the real question is: Do we actually need radios like this?
Personally, I’m not a fan of choosing radios solely based on Sherwood (5) or ARRL (6) receiver test rankings, where the primary focus is on third-order intermodulation distortion (IMD3). Last spring, I came across an article in Funkamateur, written by Werner DK1CU (1), which takes a different approach to radio selection.
In his article, Werner analyzes environmental noise, receiver sensitivity, and dynamic range—and makes the case that before choosing a radio, it makes sense to take a few measurements at your specific location. A similar line of reasoning can be found in an ARRL QEX publication (2).
Receiver sensitivity (MDS) is often highlighted as one of the most important specifications. But sensitivity is closely tied to dynamic range, susceptibility to third-order IMD, and reciprocal mixing caused by oscillator phase noise (RMDR).
Interestingly, neither Sherwood (5) nor ARRL (6) currently test for second-order intermodulation products (IMD2, where f1 + f2), which tend to be generated by strong shortwave broadcast stations. These signals are much more of a problem in Europe than in the U.S. — especially in the 6 to 13 MHz range — where the signal levels of broadcast stations are often significantly higher than those of amateur signals (see Figure 2).
These second-order products can appear as annoying “birdies and spurs” or phantom signals on the 14 and 21 MHz bands, and in some cases, strong 40-meter broadcast signals can even block your receiver entirely on 7 MHz. See Figures 1 and 2 for examples.
They also dont,t test ergonomics and audio receiver quality which is very important in a pile up.!
Figure 2 Signal strenght of broadcast stations between 9 and 14MHz
How Much Sensitivity Do We Really Need?
In real-world environments, there is always some level of ambient noise present. This noise level depends on several factors, including frequency, time of day, and—most importantly—your location. There’s a big difference between operating in an urban setting versus a quiet rural area.
Environmental noise adds directly to the receiver’s internal noise floor, which in turn limits both sensitivity and the dynamic range of the receiver.
(See Figure 3)
Figure 3: Statistical Distribution of External Noise vs. Frequency
As we can see in Figure 3, external noise is highly frequency-dependent. For example, if we take a mid-range noise level between the "B city" and "B quiet" curves from the chart, we get approximately NF = 65 dB at 1.8 MHz and NF = 40 dB at 14 MHz. This environmental noise adds directly to the receiver’s own noise floor—especially at lower frequencies—thus limiting both sensitivity and dynamic range.
Let’s calculate the total noise floor of a receiver at two different frequencies, assuming a CW filter bandwidth of 500 Hz (which corresponds to +27 dB), and using the thermal noise floor of a 50-ohm resistor at 20°C, which is –174 dBm/Hz.
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NFrx (1.8 MHz) = –174 dBm + 27 dB + 65 dB = –82 dBm
→ Total receiver noise at 1.8 MHz -
NFrx (14 MHz) = –174 dBm + 27 dB + 40 dB = –107 dBm
→ Total receiver noise at 14 MHz
After doing these theoretical calculations, I wanted to see how much noise is actually present at my own receiver , using my real antennas and location. So, over the course of more than two weeks, I used a spectrum analyzer to measure noise levels in various bands—morning, midday, and evening.
The result was an averaged external noise profile for my location JN76DA, shown in Figure 4:
| Frequency (MHz) | Noise Level (dBm) |
|---|---|
| 1.8 | –84 |
| 3.5 | –73 |
| 7 | –99 |
| 14 | –108 |
| 21 | –125 |
| 28 | –122 |
From the
measurements shown above, we can see that the theoretical noise floor I
calculated earlier differs from the actual measured values on my antennas by
only about 3 dB—a relatively small difference. The only exception is
the 3.5 MHz band, where the noise level is at least 10 dB higher,
likely due to some local interference.
What actual
signal levels are present on my antennas?
Are we perhaps overestimating the strength of received signals when designing
or testing receivers?
To answer
this, I decided to measure real-world signal levels during two of the most
extreme contest scenarios:- CQWW CW 2019
- CQ 160 CW 2020
Once again,
I used a spectrum analyzer connected directly to my antennas, performing
measurements across all bands from 1.8 MHz to 21 MHz. Unfortunately,
there was no activity on 28 MHz during the test period.
I repeated
the measurements at hourly intervals throughout each contest: in the morning,
afternoon, and night. Using the maximum values observed
during these sessions, I compiled signal snapshots—shown in Figures 5, 6,
and 7.
Receiver Selection Criteria
Based on the above measurements, I can now roughly define the required characteristics of my new receiver according to the following criteria:
• MDS (Minimum Discernible Signal): According to recommendations [1,2], the noise level present at our location should be increased by 15 dB to obtain the actual receiver sensitivity. Increasing sensitivity beyond this point makes no sense and in fact degrades the dynamic range.
• BDR (Blocking Dynamic Range): From the signal strength diagrams of 40 m broadcast stations, we can see that signals spaced 100 kHz away are nowhere stronger than –20 dBm (see Figures 1 and 2).
• RMDR (Reciprocal Mixing Dynamic Range): On the amateur bands, I have never received stronger signals than –28 dBm (local "big guns") during CQWW and CQWW160 contests. From this data, I calculate the required RMDR (see Figure 6).
• IMD3 (Third-order Intermodulation Distortion): The "big gun" signals have never been closer than 5 kHz to each other at a level of –33 dBm. It,s also not logical for two big guns to get so close ( 2kHz) to each other calling CQ in pile up.. Based on this data, I calculate the minimum IMD3 and IP3 requirements at 5kHz spacing.
• Blocking dB (100 kHz): The strongest measured signal from broadcasting stations in the 6–14 MHz range was at a level of –20 dBm.
Conclusion:
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MDS must vary with frequency band, ranging from –132 to –88 dBm. Increasing sensitivity beyond this range will degrade the dynamic range. From the results in Figure 4, with an added 15 dB margin, we get Table 1, which shows that the MDS should range from –132 dBm (at 28 MHz) to –88 dBm (at 3.5 MHz). To adjust sensitivity appropriately for each band, multiple attenuator stages are needed, providing at least 20 dB of total attenuation. For frequencies above 20 MHz, at least one preamplifier is required.
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RMDR (2 kHz): The strongest signal received during contests on my antennas was a local "big gun" at –28 dBm, which can increase phase noise. Therefore, RMDR (2 kHz) should be at least 85–90 dB. Sensitivity to phase noise is also the most important parameter for receiver quality.
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IMD3: Since "big gun" signals never appeared closer than 5–7 kHz to each other in all measurements, there is no need to measure IMD3 at 2 kHz, as Rob Sherwood does. Instead, I take IMD3 at 5 kHz as the reference.As a sample, I took the worst-case measurement at 7 MHz. From this data, I then defined the following requirements:
Example Calculation of Required Receiver Parameters for 7 MHz (see Table 1):
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MDS (sensitivity) = NF_rx + (–15 dB) = –99 dBm + (–15 dB) = –114 dBm
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RMDR (reciprocal mixing at 2 kHz) = MDS – strongest signal on 7 MHz = –114 dBm – (–28 dBm) = 86 dB
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IMD3 (third-order products at 5 kHz spacing) = MDS – strongest pair of signals at 5 kHz spacing = –114 dBm – (–28 dBm) = 86 dB
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IP3 (5 kHz) = 1.5 × IMD3 – MDS = +15 dBm
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Blocking dB (100 kHz) = MDS – strongest broadcast signal in the 6–14 MHz band = –114 dBm – (–20 dBm) = 94 dB
Based on the noise measurements and the above parameters, I obtained the results shown in Table 1. For RMDR calculation, I use the highest signal level on each band, while for IMD3 at 5 kHz I consistently use an input signal level of –33 dBm.
| Frequency | Noise Floor CW 500 Hz | Max Signal Level | Desired MDS | Min RMDR 2 kHz | Min IMD3 5 kHz |
|---|---|---|---|---|---|
| 1.8 MHz | –84 dBm | –28 dBm | –99 dBm | 71 dB | 71 dB |
| 3.5 MHz | –73 dBm | –33 dBm | –88 dBm | 55 dB | 60 dB |
| 7 MHz | –99 dBm | –28 dBm | –114 dBm | 86 dB | 86 dB |
| 14 MHz | –108 dBm | –38 dBm | –123 dBm | 85 dB | 95 dB |
| 21 MHz | –125 dBm | –38 dBm | –130 dBm | 92 dB | 102 dB |
| 28 MHz * | –122 dBm | –35 dBm | –132 dBm | 97 dB | 104 dB |
Table 1: Required receiver parameters for individual bands.
From Table 1, I take the maximum values for the receiver parameters, which should be:
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MDS: –132 dBm
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RMDR (2 kHz): 97 dB
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IMD3 (5 kHz): 104 dB
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Blocking (100 kHz): 112 dB
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Multi-stage attenuators with at least 20 dB total attenuation
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Preamplifier needed only for frequencies above 21 MHz
From this analysis, it is clear that at my location, I do not need a transceiver with 150 dB blocking and 130 dB RMDR. A good mid-range transceiver is perfectly sufficient. The numbers clearly show that a mid-class receiver from the middle section of Rob Sherwood’s list is completely adequate for my location. There is no need to buy expensive models such as the FT-101D MP, TS-890, Flex 6700, or Hilberling 8000A, priced at € 4000 or more.
I'd rather invest the price difference in better antennas—and still have money left over for a DXpedition to the Maldives (HI).
Since the market is full of used transceivers and prices are falling sharply, I’ve decided to wait for a good opportunity—a well-preserved modern transceiver that allows external RX antenna input, has software support and compatibility with my existing setup, and is ergonomic and suitable for small modifications (e.g., adding a panadapter or roofing filter). With a bit of patience and luck, such a radio can be bought second-hand for around € 600.
Conclusion
Radio amateurs often go for expensive rigs, influenced by Close-In, RMDR, and NPR test results published by Rob Sherwood, Adam Farson, or Peter Hart (RadCom).
But in real-world band conditions, even in the most demanding contests like CQWW, CQWPX, or CQWW CW 160m, older and cheaper radios—with minimal upgrades—can perform just fine in environments with strong signals.
A similar conclusion was reached in a study for the Bavarian Contest Club by DK4YJ.
It showed that RMDR/phase noise sensitivity is much more critical than third-order products (IMD3).
Sometimes it’s better to choose an ergonomic mid-range radio than to overspend on a high-end rig that performs slightly better on lab tests.
This, of course, applies to HF receivers. On VHF (2 m) during contests, the situation is entirely different when you are using transverter.
Unfortunately, I didn’t conduct similar measurements last year during the VHF Marconi contest, where the signals are truly extreme.
These measurements apply only to my location and antennas. Results may differ significantly if using long Beverage RX antennas.
Most often, the real source of unbearable interference is the correspondent's transmitter, which may key-click several kilohertz wide.
It’s a shame that some operators don’t know—or don’t bother—to fix their CW parameters (such as rise time) to reduce splatter.
For example, reducing CW rise time from 10 ms to 3 ms increases key-clicks by 20 dB at 750 Hz offset from the carrier.
Jeff AC0C describes this issue clearly on his website (ref. 3).
Similar problems occur in SSB contests, with overdriven compressors, overdriven final stages, and resulting broadband noise across the band.
On the receiving end, there’s no remedy, not even with a €4000 FT-101D MP or TS-890S.
In such cases, we can only rely on the technical culture of our fellow operators.
This exact situation was described years ago by Robi S53WW (ref. 7).
Figure 8 shows an example of such a poor signal recorded during the CQWW SSB contest.
Figure 9 shows, for comparison, a clean signal of the same strength.
Figure 8 : A snapshot of wide SSB signal during the CQ WW SSB contest
Figure 9 : A snapshot of two equal-strength signals in the CQ WW contest ,but with a significant difference in bandwith.
It’s also unfortunate that, due to the aforementioned tests, manufacturers tend to focus primarily on producing top-tier receivers, while the final stages of transmitters do not receive the same level of attention.
Golden Rules for Choosing a Radio Station
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Don’t buy a station based on the brochure!
Consider Sherwood, ARRl, Radcomm, ..... test,s with caution.
"Instead of relying solely on lab specs, try evaluating the transceiver by comparing it side by side with a reference station, as I described in my blog post 'Comparison of Yaesu FT-2000 with build -in roofing filter with Kenwood TS 890S in ARRL 2025 CW competition."
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Avoid buying a transceiver that’s just hit the market!
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Don’t test the transceiver at the dealer's shop.
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Don’t be fooled by "bells and whistles." The panorama should be displayed on a PC. Even a "touch screen" can cause issues if you have wet fingers Avoid buying a station from a smoker.
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If possible, borrow a transceiver you're interested in and test it at home with your own antennas, over the weekend or during a WW contest.
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Preferably, the transceiver should have a built-in power supply.
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It's crucial to understand the protocol and what software (SW) options are available.
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If you need to purchase a power supply opt for a linear one with transformer , not a "switcher."
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The station should have an integrated tuner, dual antenna connectors,separate receiver connector and, ideally, an RF preselector.
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If you’re buying from a dealer, does the transceiver come with service support?
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The best time to test the receiver is in the evening on 7 MHz, not in the morning.
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The ultimate test of a transceiver is the CQWW 160m contest or the UKV Marconi CW contest , ideally in a contest environment.
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For your first transceiver , consider buying a second-hand one. The prices of used equipment tend to drop over time, similar to how used car values depreciate. Later, once you will have more experience and if you participate in contests, invest in a new transceiver according to reason.
Don’t overestimate technical requirements. If you’re not a contester a mid-range transceiver on Sherwood scale priced around $1,200 is more than adequate. Ergonomics are far more important.
References:
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Werner Schnorrenberg DC4KU, Antenna Noise in the Shortwave Range – Funkamateur FA 12/14, pages 1290–1291.
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QEX May/June 2002 by G3RZP: HF Receiver Dynamic Range: How Much Do We Need?, pages 36–41.
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Jeff Blaine AC0C: https://ac0c.com/main/page_gear_mods_filter_failure.html
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BCC – Bavarian Contest Club: Dynamic Range or: How Much Roofing Does the Contester Need?
http://www.bavarian-contest-club.de/projects/hardware/Close-In-Dynamic-Range-oder-Wie-viel-Roofing-braucht-der-Contester-;art376,1772 -
Robi Vilhar S53WW: The Final Milliwatts or “Splitting Firewood at Two Meters”, CQ ZRS 6/1995
http://slovhf.net/poslednji-milivati-ali-seku-drva-na-dva-metra/
* Unfortunately, there was no activity on 28 MHz, so the signal level data is estimated at –35 dBm.
