Regency Imperial/Imperial II
By Spitfire, 441
This is the long anticipated review of the Regency Imperial AM, Double Side Band, Single Side Band Compatible Radio.
Dave and I have been playing with a variety of old tube radios since the start of Classic Radio Roundup, I have had my eye on obtaining an Imperial to add to my collection. I was really interested in the idea of owning such an early side band radio.
I found my Imperial on E-Bay, and got it for a fairly low price based on what these things usually go for on E-Bay. Mine cosmetically cleaned up well. The screened case is good condition also. It was at one time in the hands of a smoker, so much tar residue removal was the first order of business. I also cleaned out the anticipated dust from the inside.
The rig did not come with a power cord or microphone. The mike part was easy I have many D104's to use. The problem was the eight-blade old type power connector. I took a trip over to my electronics pack rat store at Zern's and scored one there. Once I powered it up, a test of all the tubes was grim. At least half of the tubes were dead and the rest didn't test very far into the good range of my tube tester. It was obvious that this radio had seen plenty hours of use. I then ordered all new tubes for the radio. I figured I wanted this radio to sound and work its best from the start. It's a definite keeper. This radio is not going anywhere. I also obtained a copy of Sam's photofact for it. I need a good road map if I want to find my way through abyss of 40 year old circuitry.
Now armed with new tubes and my Sam's Photofact at my side, I powered the old sidebander up. The radio has 13 tubes. Two of these are 6AQ5's in push pull for plenty of audio. There is one tube dedicated to the sideband circuit. I'm not exactly sure what's going on there, however, it works. The receiver tuned up real nice as expected. The radio actually transmits on both sidebands simultaneously (DSB). An early test on sideband proved this out buy confusing the hell out of one of the locals. On the receive side of things, you must choose whether you are on upper or lower sideband.
The transmit alignment didn't go as well as expected initially. Oh, the radio put out power and sounded ok. But with those two audio tubes I expected more. The power was flat, with not much forward swing. So the first on air test showed there was more work to do. It was now time to go through the circuits and replace aged and out-of-tolerance components. There are not very many electrolytic capacitors in this radio. So I replaced all of them except for the big power supply can gang capacitor. I also did some resistance checks and found a lot of resistors on the high voltage side of things were rather high in value. So with a few more hours of surgery, the rig was ready for a new radio check, 10-4.
In the meantime, I am always window-shopping on E-Bay looking for interesting radio stuff. I found a D104 Golden Eagle microphone that was being sold with a commercial VHF rig with no written description of the included microphone that stated it was a Golden Eagle, although it was clearly pictured. Now that is a mic that I thought was forever out of my price range. I really thought it would be cool to mate up with the gold-faced Imperial one of those. Imagine my surprise when I landed it for $25 including shipping.
Now back on the air for more tests. This radio is screaming loud if you want it to be. I need to run the D104 gain at less than half as well as the radio mike gain at little less than halfway up now. It is still loud and clear with 110% modulation. The radio keys at about 3 watts and will modulate to about 12 watts plus on peaks. It does the same power on side band also. I guess thatís because I am using both sidebands at the same time.
Ok, now for the post alignment performance numbers: (My own measurements, not the manufacturer's claims):
Sensitivity: .1uV (.08uV SSB) for 10db S+N/N.
Adjacent channel selectivity: 70db @ 10Khz.
I.F. Frequencies: 7.5 Mhz SSB
455 Khz AM
AM Power: 3 watts.
SSB Power: 12 watts.
AM Modulation: 110+%, 12 watts peak. ( no mod limiter)
2nd Harmonic suppression: -65dbc.
Other spurious emissions: -70dbc
I have had this rig for about a good 8 months now since it's been all tuned up. I use it quite often as it is a great performing radio and one of my favorites. I am told it could use a bit more lows in audio tone. It tends to favor the high side of the audio spectrum. That is probably influenced by the D104, which tends to emphasize the high frequency end of the voice spectrum. A different mic would likely change the radio's audio characteristics. The receiver is a pleasure to listen to. It has that nice warm tube sound. No need to turn the volume up much unless you want to hear it in while in another room in the house. The sideband audio is identical, people sound very close to being on AM. On AM the front end is very tight too. I can tell if another station is even slightly off frequency, as they quickly fall out of my pass band.
On the negative side, I haven't figured how to open the clarifier on the radio to move on transmit. I don't think it's possible without major circuit changes that I would rather not do. But it is within +/- 200 cycles on all channels. People these days are not used to locked clarifiers. I need to tell them I am using a 40-year-old tube radio. Then they become forgiving in my frequency. I did swap out the crystal for channels 1 through 4 for a crystal that gives me channels 36, 37, 38 and 40 where the local and DX sidebanders are.
I like the radio so much that I recently purchased an Imperial II.
This radio is very much the same except for small cosmetic changes. They also put the final tune knob on the side of the radio as a screw adjustment. In place of the final adjustment of the Imperial, the Imperial II has an RF gain. They also improved the receive clarifier, which they call a REC/VFO, with a geared vernier dial. This is a much nicer control. Regency also added a noise blanker that does a fair job of eliminating pulse noise like weed wacker ignitions.
The rest of the controls are shared by both versions. There is the meter switch which changes between 'S' meter, high voltage to the final, and final current in milliamps. A rather cool feature. There is the mode switch, AM, ANL, USB and LSB. Controls rounding things out are the volume and squelch. The squelch works very well on both AM and sideband. It has a nice range where you can fade out the background. Signals open it cleanly very nicely done.
I have to say I am impressed, as are others by the performance of a 40 plus year old tube sidebander.
Another on air anecdote is that I have beat out all the locals one night working "Jimmy", a "local" about 35 to 40 miles north. Jimmy says that audio is smokin'. I had the biggest grin. I love when a 40 year old tuber can outdo all those Pacific Rim radios.