by James Benedict (N8FVJ) on November 28, 2015
Many ham radio operators are familiar with the vintage tube gear in our early days of ham radio. However, more recent hams have little knowledge of tube type gear and vintage to them are older solid-state design.
Back in the early 1960s, the move from AM to SSB produced compact and lightweight transceivers. These SSB transceivers are not a true boat anchor of years past. The receiver performance is only mediocre by today’s standards. However, provide a lot of fun to operate on the ham bands. The receive tube type non-fatiguing audio quality is a pleasure to hear during good band conditions.
Choosing a vintage tube type SSB HF transceiver to meet your needs is key to the fun factor. If your ham shack is subject to a lot of man made noise on the HF bands, a quality noise blanker is important. Only a few tube type HF transceivers used a quality noise blanker. Some did not have any noise blanker option. On the other hand a quiet receiver area keeps all options open.
Modern HF transceivers have an excellent noise blanker, high dynamic range and no tune up procedure for the RF output amplifier. The digital display provides precise frequency without any drift. Instant band switching, dual VFOs and memories are taken for granted without a second thought.
The performance of the tube type HF SSB transceivers drift an average of 500Hz after a warm up period plus do not have a RIT control. Most hams will tolerate signal drift on the bands. Vintage gear nets are available for check in too. Good modern day receiver performance is considered a minimum of -133dB sensitivity, 100 KHz Dynamic Range of 120dB and a narrow Dynamic Range of 75dB at 2 KHz.
The transceivers rate from best to average. The first four transceivers are so close performance wise that any could be rated #1.
COLLINS KWM-2 Series
The Collins KWM-2 and KWM-2A are sought after and expensive. Band coverage are any 200 KHz range in-between 3.4 MHz to 30 MHz (except 5 MHz to 6.5 MHz). A crystal calibrator for zeroing the dial is included. The KWM-2 includes fourteen 200 Hz positions and the KWM-2A provides an additional twenty-three positions for 10 meters. That is a lot of crystals. New crystals are $16 each! The 134-PB noise blanker option performs well. An after market Walters rejection tuning unit will reduce or remove an interfering signal. Power output is 100 watts PEP (slightly less on upper frequency bands).
The Collins KWM-2 series has a dual conversion receiver with a Collins mechanical filter for good selectivity. Receiver performance is similar to the 75S-3 receiver with an outstanding sensitivity of -140dB, 100KHz blocking Dynamic range of 105dB and a 3 KHz narrow Dynamic range of 63dB. A separate power supply and speaker is required.
DRAKE TR-4 Series
The Drake models include the early & late TR-4, TR-4C, TR-4CW & TR-4CWrit. The frequency coverage is 80 meters thru 15 meters and 500 KHZ of 10 meters (normally 28.5 MHz to 29 MHz). The early TR-4 does not include a noise blanker option. Mid Drake TR-4 series include a hard wired noise blanker option and the late TR-4, TR-4C, TR-4CW and TR-4CWrit use a 34-PNB plug-in noise blanker. The noise blanker will remove most noise to -40dB down. Power output is 200 watts PEP.
The TR-4 series makes use of a simple single conversion type receiver. Unlike general coverage receivers, images are not an issue. The frequency dial can be verified with a built-in crystal calibrator. The TR-4 series uses an asymmetrical pair of 8 pole crystal filters (one for each sideband) providing very good selectivity due to that asymmetrical design. The TR-4CW includes a CW filter and the TR-4CWRIT has a receiver RIT control.
The Drakes had a small design issue at the mixers. The C34 capacitor on the 6EA8 (V3B) pentode grid to ground reduces the dynamic range. Remove the grounded side lead of the C34 capacitor and reconnect to capacitor C29. One side of C29 is connected to the 6EA8 cathode. Reconnect C34 to C28 opposite side that also is connected to the tuning coil. This should increase the 100KHz blocking dynamic range from 105dB to 115dB with regard to the Drake TR-4 somewhat lower sensitivity of -124dB. After the modification the Drake TR-4 should meet -124dB sensitivity, 100KHZ Dynamic blocking range of 115dB and a 2KHz narrow Dynamic range of 63. Perhaps 12BZ6 replacing the 12BA6 receiver RF amp will increase the receiver sensitivity, but may deteriorate AGC performance. One TR-4 model of the total of 12 various models used a 12BZ6 as an RF amplifier tube.
I suspect the Drake solid-state noise blanker is the best of the lot. This would make the mid & late Drake TR-4 and newer series the best for a noisy environment. A separate power supply & speaker is required.
NATIONAL NCX-5
The National NCX-5 operates from 80 meters to 15 meters and 500 kHz on 10 meters (28.5 MHz to 29 MHz was standard). Power output is 100 watts PEP.
The NCX-5 has an interesting receiver, but is missing a noise blanker option. The dial is a mechanical digital design and is surprisingly accurate. A crystal calibrator was an option. A receiver RIT is included. The NCX-5 dual conversion receiver uses two RF stages. (Before dual conversion receivers were available, a dual tuned RF stage provided better image control). An eight-pole crystal filter is used in the IF. Although rather wide at 2.8KHz @ -6dB, the 60dB specification is only 4.76KHz wide. The NCX-5 receiver should provide a superior 100 KHZ wide dynamic range if the Mixers and AGC is well designed. Some will state the 12BE6 second RF amplifier is a noisy performer. But, that is only true if used as a converter tube. I never seen the receiver specifications, but others have commented the receiver is definitely the equal of the TR-4 with the high sensitivity of the Collins KWM-2. A separate power supply and speaker is required. Owning all three transceivers, I agree.
HALLICRAFTERS SR-150 & SR-400 Cyclone
I combined both radios due to similar performance, but the SR-400 is the upgrade and expensive like the Collins KWM-2 series. Some will comment the SR-400 is in a different league compared to the SR-150. Both transceivers cover 80 meters thru 10 meters (28.0 to 29.5 MHz). Both transceivers have a receiver RIT. The SR-400 output 275 watts SBB & 200 watts CW and the SR-150 output is 150 watts PEP & 125 watts CW.
Both receivers are a dual conversion design with an IF crystal filter. A built-in 100Hz crystal calibrator is standard. The receivers are reported to be very quiet. I never saw measured specifications. A separate power supply and speaker are required.
SWAN 350, 500 & 700 series
The Swan transceivers operate 80 meters thru 15 meters plus 28.5-29.0 MHZ on 10 meters. RF power output varies from 250 watts PEP/150CW to later models producing 300 watts PEP/200 watts CW. The base 350 model does not include a calibrator or noise limiter. The 350A did include a crystal calibrator. The noise limiter is likely a diode based audio clipper circuit and performance on SSB is poor. Perhaps the latest models had a true noise blanker.
The receiver is a simple single conversion design with an eight-pole crystal lattice filter. A series called the SS special used two eight pole crystal filters for better selectivity. A tag exists on the front panel identifying these models. I owned a Swan model 350 and found the receiver more noisy vs the Collins, Drake & National. I never saw receiver specifications, but suspect -133dB noise floor, 100KHZ Dynamic range of 85dB and narrow 5KHz Dynamic range of 60dB. A separate power supply and speaker is required.
HEATHKIT HW-100/101, SB-100 thru 102 series
The HW and SB series were about identical design wise. All models provide 80 meters thru 15 meters and 500kHz on 10 meters. Unlike the hard-wired transceivers listed above, the Heathkits were based upon using cheaper phenolic circuit boards. Some heat and moisture issues caused problems over the years, but did not make for unusually high reliability. A kit is difficult to build even with most of the wiring on the circuit boards. Power output was 100 watts PEP/CW.
The receivers were double conversion using an eight pole crystal. Performance is similar to the Swan 350, 500, 700 series, but the double conversion receiver is perhaps a little less noisy. A noise limiter was not included and an optional crystal calibrator was available. The tuning dial may slip after the years. A separate power supply & speaker is required.
SWAN 270 CYGNET
The Swan provides 80 thru 15 meters with 500KHZ on 10 meters. Power output is 100 watts PEP/CW. A crystal calibrator or noise limiter is not included in the design. A noise limiter is about useless on SSB.
The receiver is a single conversion design. Performance is the same as the Swan 350 series. The power supply and speaker is built-in. If the additional power output of the larger Swans is not desired, I would prefer the Swan 270.
ADDITIONAL COMMENTS
The top four transceivers outperform a Yaesu FT-101E IMO. Quieter receiver, better narrow dynamic range performance and the AGC is lacking in the early to mid production Yaesu FT-101. The Yaesu noise blanker was improved in the later series.
Replacement tubes can be expensive. With regard to receiver tubes, eBay is not always the best price. The 12BE6 & 12BA6 averages $6-8 on eBay where as a few tube dealers in FL sell NOS for $4-5.
If performing self service, be aware of the dangerous high voltages.
None of these transceivers included a speech processor. The Turner +3 desk microphones have a great performing built-in audio compressor. Loud, but not overbearing or distorted plus not a tendency to over modulate.
The tube type higher RF output transceivers may help a little on 80 & 40 meters. Even 1/2 an S unit out of the noise makes a difference.
Keep in mind these classic tube type transceivers are fun backup classics. If only affording one HF transceiver, I would rather own a FT-747GX, IC-735 or an Alinco DX-70. But, these old tube types make warmth like a pet and seem to have a soul.
Feel free to correct any errors and add info. Plus recommend other classics not listed.