Mattโs Rooftop Receiver Melee, Part Two
By Matt Blaze
You may remember that back in April I hauled eight of my favorite receivers up to my roof and hooked them up to a portable antennas and compare their ability to demodulate various signals simultaneously. In most cases, the similarities between radios are more striking than their differences. I hinted that there would be a second part, including more receivers and more challenging signals, to further reveal and highlight the actual real world performance differences between the radios we use.
This time, I used roughly the same setup, but with a total of 15 different radios. This time, I took advantage of the good weather and brought a bunch of receivers, recording equipment, cables, and antennas to my roof to listen and record shortwave signals under the open sky.
Our 15 receivers range from 1980s "dream radios" to current production desktop models, to less expensive modern portables, to high performance benchtop laboratory measurement equipment. I tried to collect samples of various radios that you may be familiar with and those that you may not be familiar with. The
lineup includes:
Icom R-8600, the current production "DC to Daylight" (or at least up to 3 GHz) general coverage communications receiver with highly regarded shortwave performance.
AOR AR-ONE, another DC to 3 GHz universal coverage radio receiver , is little known due to its high price and limited availability in the United States. In my opinion, the performance is excellent, but the counter-intuitive and clunky (menu-driven) user interface is not ideal for shortwave.
Reuter RDR Pocket, a very cute, if almost impossible to buy in the US, low volume, high performance SDR based shortwave portable receiver. It has a great spectrum display and packs near-desktop performance into a surprisingly small package.
AOR 7030Plus, a highly regarded mobile/desktop HF receiver from the late 90s. digital, but retaining some important analog-era features such as mechanical filters. Designed and (mostly) manufactured in the UK, it has a quirky menu-driven user interface, but it's fun once you get used to it.
Drake R8B, the last of the beloved Drake receivers. Probably the main competitor to the 7030+.
Drake R7A, a great analog communications receiver (but with a digital VFO) from the early 80's. It still outperforms many current radios.
Sony ICF-6800W, a top-of-the-line "speaker box" consumer receiver from the early 1980s. Great radio, but difficult to use on SSB, as we saw in the first round.
Panasonic RF-4900, the main competitor of Sony . Anchor form factor, but (unlikely) can run on internal D cells. Performance on AM is generally impressive, but as with the Sony 6800, it's difficult to tune on SSB.
You may remember the above radio from the first round back in April. The new radios this time around are:
Tecsun 501x, a larger format LW/MW/HF/FM portable released last year. As discussed below, it generally performs well, but is unfortunately susceptible to intermodulation when connected to a wideband external antenna (as we will see in part one).
The Tecsun PL-990x, a small portable (updated PL880), has many of the same features as the 501x. Like the H501x, performance as a standalone radio is good, but susceptibility to intermodulation when fed with an external antenna is disappointing.
The Sangean ATS-909x, a recently launched LW/MW/HF/FM portable, has a good reputation but has some quirks, such as only a relatively narrow IF bandwidth selection on HF. Works great on external antennas.
Sangean ATS-909ร2, an updated current production version of the ATS-909x, with the addition of air bands and some performance improvements. Overall very good, although I would have preferred a wider IF bandwidth option. My go-to travel receiver if I donโt want to bring the Reuter Pocket.
The Sony ICF-7600GR, a small digital LW/MW/SW/FM portable device introduced in 2001, is the last of Sony's shortwave receivers. Showing its age but still competitive in performance.
Belka DX, the smallest radio in our range, made in Belarus. You will love or hate the minimalist interface of and (one knob and four buttons). This is a great radio to have if you want to secretly copy digital stations in your hidden spy lair. It may be difficult to obtain now due to sanctions.
Finally, something a little louder: Narda Signal Shark 3310, a high-performance SDR-based 8.5 GHz RF spectrum and signal analyzer. As with most test equipment like this, demodulation (especially HF mode) is an afterthought. But it has an excellent front end and dynamic range that can be used to identify, extract and analyze weak signals even in the presence of strong interference. Not cheap, but it's intended as measurement-grade lab equipment, not consumer equipment. Due to the multi-stage DSP signal path, the demodulated audio is significantly delayed (hundreds of milliseconds) compared to other receivers.
The antenna is my portable "signal scanner" on a swiveling tripod Wellbrook FLX-1530, using a power splitter and a pair of Stridsberg Engineering 8-port HF distribution amplifiers to power 15 radios. Therefore, each radio has very close to the exact same signal at its RF input.
recordings are taken directly from each radio's line out jack (if available) or from the external speaker/headphone output. In either case, the audio is fed through an isolated interface and converted to a balanced signal for recording.
each radio as well as a stereo track where I compared the audio from each radio (one after the other) to the Icom R8600 reference, the R8100's audio on the left channel and the other radio's audio on the right channel. Stereo tracks give you a quick overview of what all your radios sound like.
If you've never heard one of my comparisons before, stereo recording needs some explanation. For this to make sense, you have to listen to stereo using decent headphones if possible. You can switch the earpieces back and forth (holding your finger on pause and rewind) to get a quick sense of how each radio sounds compared to "known" receivers, and how they handle issues like attenuation and static.
Solo tracks, on the other hand, consist entirely of continuous audio from a single radio, without narration or interruptions. You can use them to gain insight into the performance of a specific radio you're interested in, or to compare different receivers against each other.
As with the previous round in April, I recorded three different HF signals over two days, making a total of three 15-way comparisons. Like last time, I think some of the performance differences and similarities might surprise you.
It's worth noting that this is not intended as a lab test to measure receiver parameters, but rather to describe how different receivers demodulate a real signal from the antenna jack to the speaker in practice. Measurements of receiver specs are great for understanding quality differences (and are widely available as published specs), but they don't always tell us the whole story about how well we're able to understand and enjoy the actual signal we capture.
Part One: A pretty good signal from Spain
Our first signal was an external service from Radio Spain, captured in the late afternoon at 17855 KHz . Signal is generally good, with occasional deep attenuation. All receivers can demodulate signals easily, but there are differences in audio quality and response and recovery from attenuation. I set each receiver to the widest reasonably available IF bandwidth (up to 8 KHz), which provided the best overall audio quality.
Pay special attention to the occasional extra station audio in the capture of the two Tecsun radios (especially audible around minute 9), which is caused by the intermodulation mix produced in these receivers (I was able to pass the attenuator switch reduces but cannot completely eliminate).
Part Two: A Weak Signal from Brazil
Radio Voz Missionaria is a low power (5-10 kW) Portuguese-speaking Brazilian religious radio station that broadcasts via shortwave to remote areas of Brazil. The 9665 KHz transmitter is actually on 9667 KHz (an unusual mistake for a licensed broadcaster).
North America is definitely not in the expected coverage, but the signal is often heard here. Tonight it was detectable but very trivial, providing a good opportunity to see how each receiver can or cannot handle signals close to noise. Most radios are able to detect something at least some of the time, but the clarity varies.
Part Three: A Mild Signal from Cuba in a Crowded Band
Like it or not, Radio Havana, Cuba is undoubtedly one of the highest rated shortwave radio stations in North America. Their signal was pretty good here tonight on 6165 KHz, but over 5 KHz on 6160 was a slightly stronger signal from WBCQ (which I may have misidentified as WRMI in the aside). This provides an ideal opportunity to listen to the receiver's ability to handle adjacent channel suppression under real-world conditions. The receiver bandwidth is (where possible) set to the widest available setting to best avoid overflow of the WBCQ signal.
A few notes about the review:
Everything was done on my roof and took a few hours to move the equipment. But the effort is worth it; listening to the radio in the open air is a different experience. Recordings were made using a 32-channel Sound Devices โScorpioโ recorder with an SL-16 mixing console. 15 radio audio channels are isolated and converted to balanced outputs via a series of Switchcraft 318 direct interface isolation boxes (ideal for recording multiple radios using professional audio equipment ). I monitor with headphones so I can get critical tuning in and avoid disturbing my neighbors. Like most radios, the recording equipment is battery powered to help avoid line noise and ground loop failures. The
stereo track narration was done by me in real time as the signal was being recorded. There is no post-production other than converting the various tracks to mp3s. I will occasionally comment on receiver performance and a few other things, and those comments may not always reflect the conclusions I later come to after careful listening to the solo tracks. But please use your own judgment. I used a Coles "lip" mic, an unusual (and very useful) ribbon mic designed decades ago for BBC for use in high-noise environments (and still made today). It has been very effective at reducing the sometimes noisy street noise, birdsong, and other ambient outdoor sounds in my neighborhood. Microphone preamp is Sonosax M2D2.
Thanks again for listening and 73!
source: SWL post
Uncle is here:
Regarding the evaluation of the great Matt Blaze, what do you think? Comments are welcome!
