Classic Status: 23 channel.
Appeal: Owned by friends.
Condition: Cosmetic, Good. Electrical, Good
Acquired: 2006, E-Bay
This is my Royce 640 23 channel SSB/AM base radio. As can be seen in the picture, this radio is chuck full of knobs and features, all packaged in a handsome wood grained case. All of this was highlighted with green backlit meters and channel selector which altogether made for an aesthetically pleasing package that was a pleasure to sit in front of. The 640 employs a fairly typical single conversion SSB, dual conversion AM receiver, with pulse gate noise blanking, and a curious feature which allows the user to selectively disable the AGC. The plethora of features made this a popular radio in the mid 70's. I knew at least 4 people who ran them, and they all sounded good on transmit, both AM and SSB. My familiarity with this rig, plus a vivid memory of my envy of three of my radio friends who each managed to get one, while I languished with a second hand AM-only Lafayette, qualifies this as a "dream rig" and a candidate for my retro collection. But, as I have been finding out lately, sometimes reality can't always live up to the expectations of the dream.
The rig pictured was obtained from an E-Bay purchase, which cost me a whopping $10 (plus the ubiquitous shipping fees). The radio was in great shape, needing only a bit of cleaning, both cosmetically and internally on the many controls and switches which had become a bit scratchy and intermittent from 30 years of accumulated tarnish. After the rig was thoroughly cleaned, I went through the schematic and made a couple of modifications. I first dropped the AM transmit power back to 3 watts from over 5, so that transmit modulation would make the full 100% without flat topping. I also extended the range of the Clarifier control. On the PC board there is a jumper option to select one of two tuning ranges. From the factory, the radio will only move about +/- 800 Hz. Moving the jumper to the other pin, extends that range to about +/- 2 Khz, which allows for the ability to follow some of those more "off-frequency" stations. When the mods were complete, I gave the rig a complete alignment including netting the crystal frequencies. Happily, I found that all of the crystals were within easy tuning range, so no replacements were needed. The receiver was very strong, besting even my Hy-Gain 623 and coming pretty close to my Tram D201in overall receiver sensitivity, and equaled the Hy-Gain in adjacent channel rejection. But those numbers tell only part of the story........
Here are the post alignment performance specs (My own measurements, not the manufacturer's claims):
Sensitivity: AM .26uV for 10db S+N/N.
SSB .15uV for 10db S+N/N.
Adjacent channel selectivity: 60db @ 10Khz.
I.F. Frequency: 1st: 11.275Mhz 2nd (AM Only): 455 Khz
AM Power: 3 watts.
SSB Power: 15 watts.
AM Modulation: 100+%, 12 watts peak .
2nd Harmonic suppression: -60dbc.
Other spurious emissions: >-70dbc.
The following is my subjective opinion of the Royce:
This rig, being such a visually attractive radio, really made me really want to enjoy using it. However, there were a few little "issues" which made the reality of operation a much different picture than the idyllic illusion generated by the radio's simple ergonomic charm. The biggest issue that I have with the radio is that the receiver seems to be very noisy. On any given day, I can turn this rig on and the noise level on the "S" meter never drops below S4. On other radios (Like the aforementioned Hy-Gain) I normally see S1 or less noise levels. But the Royce isn't the only radio that does this. My "fancy" H.F. ham rig, the Icom 706 also seems to show a great deal of noise on AM receive. I'm not sure what it is that I am witnessing. Is it truly noise or just an overly generous "S" meter's indication of it? At first I was convinced that the noise level was a result of the Royce's design being particularly vulnerable to locally generated computer network noise. But even if I switch all the network equipment off, I still see a noise level (albeit close to 1 "S" unit lower). The receiver is pretty hot as the bench numbers reveal, but there is no sign of noise indication when hooked up on the test bench. It only appears when the rig is connected to an antenna. Could it just be that this rig just "hears" better? There is also the calibration of the "S" meter to consider. .5 uV of signal, which on some radios is the point of minimal sensitivity, will show up as an S1 reading on the 640's meter. The meter then increases at a rate of only 3-4 db per "S" unit up until about S5 (A properly calibrated "S" meter should see close to 6 db per "S" unit). From there on, the amount of signal required to move an "S" unit increases proportionately until it reaches close to 8db /"S" unit by the time it hits S9 (50uV). The relatively "loose" low end of the meter could account for the "noise" that I am perceiving. I will need to do some more A-B comparisons with other rigs on weaker signals to see if they can be heard through the "noise" on the Royce, as well as they are heard on other rigs, which do not seem to exhibit a perceivable noise problem. In any case, the noise can usually be silenced by backing off on the R.F. Gain a little or using the squelch, and that segues nicely into my next beef with this radio, the squelch circuit. On the 640, the squelch action (opening or closing) is accompanied by an objectionable "pop" in the speaker. There is also not enough hysterisis, which results in frequent squelch popping on every little spike in noise or signal. I am used to (and much prefer) the squelch actions displayed by my tube rigs and some of the better solid state units, where the receiver smoothly transitions from squelched to unsquelched. I tried adding some capacitance to the squelch circuit to both add some hysterisis, and to smooth out the squelch action. By doing this, I managed to "dull" the pop, but not completely eliminate it. I also noticed that the squelch works better if the AGC button is turned off. But then a station who normally shows a signal of S9, now pegs the meter hard, which is not a state that I want to keep the radio in. And since we're on the topic of meters, my last little beef involves Royce's choice for meter functions. While the Royce has 3 nicely lit and easy to read meters, why did they feel the need to use separate meters in order to read both the forward SWR calibrate reference power, and reverse SWR simultaneously? If it were me, I'd have made the forward calibrate meter a modulation meter instead and just switch the SWR functions on the 3rd meter like most other radios with built-in SWR meters do. Another really small nit-picky issue relates to the power-on switch and the power supply itself. The front panel "On/Off" button only interrupts the D.C. side of the power supply, so that even when the radio is "off", the internal power supply is allowed to keep running (wasteful and hot). To turn off the A.C. side of the supply, you have to utilize the Auto/Off/On switch next to the clock.
Receiver interference immunity performance was about average. Adjacent channel rejection was excellent, comparing favorably to more expensive rigs like the Tram D201 and the Hy-Gain 623. However, it was much less immune to front end overload, and the Royce could hear "bleed" from strong local stations that was not present on the more premium rigs.
But all is not bad, despite my critical observations. Receive audio is nice and full, despite the speaker aiming out from the bottom of the rig. Transmit audio is also very nice. It's clean and has a good tonal quality, both on AM and SSB. The transmitter spectral purity is among the best of all my retro radios, with only 2nd and 3rd harmonic content visible, and then, only at -60dbc, which is better than the specs of the time called for. This may have something to do with the doubly balanced diode mixer circuits that this rig employs, which are better than the usual straight mixer. The radio also includes a unique final protection circuit, which will shut down the transmitter if it senses an SWR above a certain (adjustable) point. But there is both good and bad in this. On one hand, this circuit will protect the radio's final transistor from failure at the hands of high SWR (a problem that seems to be more myth than reality). On the other hand, if you are running SSB, and using an external amplifier or receive pre-amp, which utilizes R.F. sensing circuits, for the brief period of time when the amp's R.F sensing relay unkeys during low power voice lulls, the protection circuit can sometimes see a momentary high SWR as the relay switches or chatters. This can cause the protection circuit to trigger, shutting down your transmit until you unkey to reset it. In the past, the guys I knew who ran these rigs used to run their mic audio level up enough that background noise would keep the power high enough to prevent the amplifier relay from unkeying. Of course, it's not a difficult task to defeat this circuit if it becomes a problem.
In conclusion, Royce did a nice job producing a deluxe base radio. All things considered, it's a good performer. It compares favorably against my Midland 13-885, and SBE Trinidad in overall performance. You really can't realistically expect it to compete toe to toe with radios which cost hundreds of dollars more, and not come out with a few bruises. And the radio really IS nice to look at. I will continue to try to correct some of the rig's minor design ills, and hopefully it will become one of my favorites.