Few months ago I bought on eBay a vintage Chinese military HF receiver 339HF. The radio was supposedly old-new-stock, still in its original box, and came with service manual (in Chinese, of course), two sets of headphones, lot of spare parts (transistors, capacitors, fuses, light bulbs), wire antenna and a backpack (the
radio weights nearly 30lb).
After two months shipping time, the radio finally arrived more than a month ago. It definitely looked old and there were visible signs of some moisture damage, corrosion, and also some damage to the radio case probably due to a fall in tranport. So I wasn't very hopefull and let it sit in the box until yesterday, when I found time to unpack it, clean it, and put it work.
What a pleasent surprize!!! This radio is great.
Few words about the radio itself. It's a military receiver built in 1976. Fully solid state, analogue tuning and display, coverage from
1.5 to 30 MHz, in six bands, frequency readout down to 1 kHz. Dual conversion, four IF filters - 6, 3, 1 and 0.4 kHz - AM, SSB and CB modes. Only one AGC position (somewhat fast judging by ear) and OFF, manual RF and IF gain (I guess based on what the knobs do, as both the manual and all signs on the radio are in Chinese), manual adjustment of beat frequency. Two headphone sockets, but no speaker. Only one antenna input (high Z), but comes with an
accessory impedance matching transformer to connect low Z antenna. Has one additional control knob that must be some kind of antenna
tuning circuit, as it has an air capacitor, but does not seem to behave like fine tuning, it rather improves sensitivity based on
behavior of the S-meter. The S-meter does not have any scale so it is only a relative indication of the signal strength, and it also
can be used as battery voltage meter when the AGC is OFF. The radio can be powered with 10 D-cells in a removable drawer, or the battery
tray can be replaced with an removable AC-to-DC power supply which is switchable for 220 or 110 V AC. The case is typical military constuction, thick aluminum painted camuflage green, with a sealed and clamped cover for the front panel. It is not truelly waterproof but definitely a different class from any consumer or amateur
equipment. The interior is mounted on a solid cast aluminum chassis. Everything is very solid and "oversized", and somewhat "crude" by modern Western standards - while it is not pretty, it is definitely very robust and functional. The tunning mechanism is a complex gear transmission. The different functional blocks inside the radio are fully modularized and individually shielded. Net, a completely different standard of design and construction compared to what we see in today's "disposable"
consumer electronics.
So yesterday I finally took the radio out of the box and started cleaning. Also the external case was rather dirty and with visible marks of mositure, the interior looked clean. The AC power supply was heavily correded on the exterior, as well as the battery trays
and the headphones. I spent several hour cleaning it piece by piece with isopropylic alcohol (for a lack of any better idea). Finally
when I judged that the radio and the accessories were clean enough to minimize the risk of a short circuit (and hopefully a case of bird flu for the user), I decided to power it up, first with batteries and then AC.
Frankly I wasn't expecting the radio to function, at least not 100%. Contrary to my expectations, the radio works perfectly and
still have not found a single problem. I hooked it up to a 40ft wire antenna and decided to compare it side-by-side with the Palstar R30CC.
So how does this piece of old Chinese military metal compare with a modern receiver? Surprize, surprize, the 339HF not only matches, but is some aspects it actually beats the R30. Here is my subjective review:
- Sensitivity: The R30 is clearly more sensitive, but in practice with the 40ft wire antenna it only translates in more atmospheric
noise. Even with no signal and a long antenna the R30 S-meter reads at least S-3 on the lower bands (5-10 MHz), and the atmospheric
noise is clearly audible and rather harsh. On the other hand the 339HF is a very "quiet" receiver, with much less background noise
when no signal is present. During 3 hours listening session I could not find a single weak station (that would barely stand out from the
background noise) that would sound better on the R30. On the contrary, seveal very weak signals actually sounded better on the 339HF (see more below under audio recovery).
- Selectivity: The acid test was Radio Universidad from Mexico City (weak signal from 10kW transmitter on 6185kHz) right next to Radio
Nederlands on 6190kHz from Surinam. On the R30 Radio Universidad was only intelligeable using LSB and narrow filter. In AM, with the
wide filter, the powerfull Radio Nederlands would complete "swamp" the weak signal, while with the narrow filter the audio was so
muffled that it was very hard to understand, yet still with some signs of interference. The 339HF 6kHz filter would produce similar results at the R30 wide filter. However the 3kHz will produce a
signal of similar clarity as the R30 on LSB, but more pleasant to the ear. Using SSB on the 339HF did not produce any significant advantage over the AM mode.
- Dynamic range: The 339HF can definitely accept the 40ft antenna without a slightest sign of overloading. I have not detected any images either. The only "defect" found so far is that a local AM station on 870kHz, which transmitter is only a mile or so from my house, leaked through somewhere around 9MHz - strangly enough it was
a weak but very clear and "narrow" signal which could be tuned as if it was a distant SW station.
- Audio recovery: This is an area where the 339HF really shines. The audio is very pleasent, with a nice balance between bass and
treble tones, no harsh noises, and somewhat mellow, very much like an old tube receiver. It is definitely much nicer than the R30 which tends to sound harsh on very weak signals and during fading. Although in absolute terms the audio recovery for weak DX signals is about the same on both receiver, it sound more pleasant on the 339HF resulting is less "listening fatigue" after extended period of time. The only radio I have used so far which I would give a similar audio quality as the 339HF was the Lowe HF150.
- Ergonomics: Although the frequency readout is down to 1kHz, the scale is somewhat misaligned and now the radio misreads anywhere by 20 to 50 kHz depending on the band and frequency. Of course the scale can be aligned, and I will probably do it if I find somebody who can translate the service manual for me. However, it is very repeatable and stable. I have noted down the offset vs. WWF on each band I could test, and once the difference is taken into account I
have noticed less than 1kHz drifting or change after 3 hours of operation. I repeated the test today, and after approx. 30 minutes warm-up the offset is consistent with yesterday's tests. The knobs are scattered around the front panel in somewhat strange pattern at first look, but after some time the operation is very logical and
intuitive. All the knobs and controls are large, and although somewhat stiff, they are very easy to adjust and have a very solid feeling. SSB operation is somewhat more difficult than with the R30 due to the manual beat frequency adjustment, but very usable with a little bit of practice.
I connected the radio to an external audio amplifier and the sound through large speakers is as good as I can remember from any radio I
have used or listened to.
Net, a very pleasent surprize and this radio has instantly become my favorite DX machine. In terms of selectivity and dynamic range it sounds as good as the R30CC, while the audio is as nice to the ear as the Lowe HF150. It beats the HF150 and the Sony 7600GR when it
comes to strong signals and large antennas.
I hope it will last "forever", which may not be such a outrageous expectation, as it has come out working perfectly after 30 years of sitting in some Chinese military warehouse, where is was obviosly subject to less-then-ideal storage conditions judging by the widespread corrosion of exterior metal surfaces, and moisture damage
to the canvas bag, cartons, manual and all rubber or plastic surfaces.
For the technically-minded, few words about the circuit architecture.
The RF signal passes through a bank of six sub-octave tunable bandpass filter (one for each band), then through a first RF amplifier, then again through another bank of bandpass filters, than through a second RF amplifier, and then again through a third bank of bandpass filters. Then the RF feeds a first mixer with 1335kHz
IF, passes through a crystal filter and first IF amplifier, than follows to a second mixer with 465kHz IF, and then through three selectable crystal filters (nominally 6, 3 and 1 kHz). The CW mode with 400Hz bandwith is just an audio filter which works together with the 3kHz IF filter. The AGC acts on the second IF amplifier,
and can be turned OFF or adjusted manually. Then the signal feeds a product detector which can be fed from a manually tunable beat frequency oscilator for SSB and CW signals. Finally, the audio is fed to a simple audio amplifier.
Interestingly each functional block (each bandpass filter, RF amplifier, IF amplifier, mixer, etc.) is build on a separate PCB and
can be replaced individually. Also, each function block is individually shielded. Makes troubleshooting and field repairs a no-
brainer. The each functional block has a detailed description in the manual, and spare transistors, diodes and capacitors are
provided in the spare parts lot that came with the radio. Even a moderately trained tech can troubleshoot and repair the radio (providing that he can read Chinese, off course). All components are fairly large so replacement with basic tools is easy (no surface mounted components).
The circuit is extremelly simple and "transparent", and the several cascaded tunable LC circuits in the RF path result in very good strong signal capability. Also, because the signal goes through the LC bandpass filter ahead of the first RF amplifier, the radio must be pretty immune to damage from static.
In the meantime, I did a little bit of research and here is what I found:
The Chinese have produced a family of "portable" HF receivers for field use which were all designated with x39HF. Of course, they must have made more models, but finding info about communist China equipment is not all that easy.
The first of the family was the called 139HF. It has somewhat limited frequency coverage in three bands. It is rather well known in the USA because this receiver was used extensively by the Vietcong to monitor American HF transmissions during the war. Several were captured and brought to the USA, and can be found in museums or collections. If interested, these links make a good reading:
http://www.armyradio.com/arsc/customer/pages.php?pageurl=/publish/Articles/William_Howard/North_Vietnamese_Army_Comms.htm
http://www.armyradio.com/arsc/customer/pages.php?pageurl=/publish/Articles/William_Howard/chinese_type_139_a_radio_receive.htm
The next radio in the family was the 239HF. It has full coverage from 1.5 to 30MHz in six bands, and is a dual conversion receiver with substantially better performance than the 139HF. It was made in big quantities in the 1960's. The quality was supposedly quite good, and some of these receivers made it to the US and Canada. Generally, this radio is regarded as a good mechanical quality, rugged receiver, but with inferior performance to contemporary Western radios. I obtained a copy of the circuit diagram of this receiver and compared to the 339HF that I bought, it definitely looks like an inferior performer. It uses LC filters in the IF stage so selectivity can not be that great. Please note that I have not used this radio, so it is a very superficial evaluation based on word-of-mouth and some analysis of the circuit diagram.
The newest of the three is the 339HF. It is also a dual conversion receiver, and for more technical details please see my previous post. The main differences vs. the 239HF are:
- The 339HF has a three-step tracking preselector with two amplification steps before the first mixer. The 239 has a two-step preselector, with only one amplification step.
- The 339HF employes crystal filters in both IF stages, while the 239HF has LC filters.
The Canadian collector I exchanged some emails with is of the opinion that the performance of the 339HF is significantly better than the 239HF, but the mechanical quality is not as good, making the 339HF a less desirable radio from a collectors standpoint. The 239HF is also older what makes it more valuable on the antique market. However as I was looking for a radio that I am intending to use, I decided to get the 339HF.
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