Two Letters Re: Older Technology Radio Receivers (Original Thread Title Was: Crystal Radios)

Mr. Rawles;
I have been monitoring the latest posts on vintage radios–pro and con–and decided to offer more information and a possible solution for SurvivalBlog readers considering vintage electronics.

M.E. is spot on in his post about the relatively anemic performance of crystal radios versus superheterodyne (as all “American Fiver” sets are known) tube radios. The biggest issue with crystal sets is their absolute lack of range. During a severe crisis, local radio stations will most likely be forced to regurgitate propaganda resulting in little, if any, useful information. As is generally known, news from afar (Canada, Australia, Europe, etc) offers the best advanced information of what will most likely be occurring regionally in our country during an extreme crisis; either government sanctioned-such as the swine flu or unexpected-such as another massive terrorist attack on our soil. This being the case, crystal sets will be useless for all intent and purpose. Regenerative sets will generally fall in this category. An added caveat of regenerative sets is the constant adjustment of the power supply (referred to as a “tickler coil”) by the user. In short, Regen Tube sets require the operator to adjust a variable resistance control to achieve high gain. Unfortunately, the gain qualities would be somewhat unstable requiring the operator to constantly keep the control (tickler coil) just short of oscillation.
Although fine-tuning a regen radio would be possible with time and experience, most of us in a high stress situation have more pressing matters and would prefer a plug-and-play device that can be dialed-in and easily monitored in an attempt to extract pertinent information.

As is often the case, the more information one has, the more complicated the matter of choice often becomes. My advice is simple: if a reader is looking for a radio with unmatched abilities it would be the Zenith line of Trans-Oceanic Radios. These are more than just simple Standard Broadcast ready radios. Zenith Trans-Oceanics are capable of picking up shortwave broadcasts from all over the world.
These radios offer standard broadcast (550-1600 AM), 4-9 and 2-4 MC shortwave (some models have a slightly different bandwidth for these ranges but it is really a non-issue) 16 MC shortwave, 19 MC shortwave, 25 MC shortwave and 31 MC shortwave.

One has to understand that Trans-Oceanics were designed for use in WWII to be utilized by the U.S. Signal Corps for the monitoring of both enemy and ally transmissions. Suffice it to say, any radio good enough to help the boys from the Greatest Generation win WWII will perform beyond expectations!

As an example, I am ensconced in a small town in northern Idaho completely surrounded by mountains and can pick up stations several hundred to several thousands of miles away. I listen to radio
stations from San Francisco, Russia and Japan, Vancouver, Alberta and Quebec (Canada), Denver, Boise, Reno and Brazil (South America), Florida, Havana Cuba) and San Martinique (Caribbean). (What makes my listening experience exceptional is the fact that my mother is of Cuban ancestry and fills me in on the information coming out of South America, while my Russian wife “decodes” broadcasts from Russia.)

Trans-Oceanics are still readily available on eBay and range in price from $50-$250 as an average. All though several pages could be dedicated to the different models of Trans-Oceanics, all of them will offer standard broadcasts as well as shortwave capabilities. Tubes are still readily available and most of them will require electrical refurbishment as 50 year-old capacitors will break down. I have been restoring Trans-Oceanics for quite some time and feel that these radios offer the best of both worlds: Rugged dependability and simplicity of use. If any of your readers would like to contact me
concerning Trans-Oceanics (as I have several refurbished units available and offer discreet refurbishment services as well) please feel free to contact me via email at and I will do my best to assist my fellow SB readers prepare for the trying times ahead.

Mr. Rawles, I would like to offer my sincerest thanks for continuing to be a “voice crying out in the wilderness”. God Bless. – Prof. W.

Hi James et altera:
For some years now I have refurbished tube radios bought via eBay. I replace all the electrolytic capacitors and paper capacitors, check all the tubes. Then I tune all the padder capacitors and adjustable coils using an RF signal generator. A Fluke multimeter, a tube tester, and an RF signal generator are essential for this work. I’ve done four models of Hallicrafters and the G-500, H-500, and 600 models of the Zenith Trans-Oceanics (“T-Os”).. The 600s have provision for a dial light off a separate battery and a slide rule-like dial. One does not need the gas discharge tube voltage regulator tube in the 600s for DC use. The AM band Wavemagnet is turnable very easily. This aids in both reducing AM interference and increasing the signal strength. I like the 600s the best.

The source for parts and books is They sell an interesting little kit for a simple tube radio. Would be a great learning tool for novices.

Now while the All American AC/DC radios are a good choice, IMHO they may not be the best. Only a few receive any of the shortwave bands. I would try to locate one that does if you wish to go this route. The shortwave broadcast bands are going to be very important when the Schumer hits the fan. The Zenith T-Os cover the spectrum from 560 kHz up to 31 mHz. Now these models use the miniature 1.5 volt filament tubes that have low “A” battery drain. I fabricate a battery pack with ten of the 9 Volt small batteries in series for the “B” plate current, and 5 of the 1.5 volt “D” batteries in series for the “A” filament current. Five instead of six is preferable. The T-Os work fine with 5 “D” cells in series and the lower filament current makes the filaments last longer. The T-Os have a tuned RF stage, making them much more sensitive than the All American AC/DC designs. I plan to fabricate and test a board for charging rechargable batteries from a 12 VDC source by the following arrangement: connect two of the nine V batteries in series, thence in parallel with one D battery. Arrange five such links in parallel, then all will be charged by a 12 VDC source. One disadvantage of the T-Os is that they use a pentagrid converter tube, the 1L6, which is now hard to find. When the Schumer hits the fan, I will give these spare T-Os to my close-by neighbors.

The disadvantage of the T-Os is that they will not receive single sideband (SSB) transmissions. Most all military and government transmissions will be SSB. The range of an SSB signal is greater. For SSB reception I recommend one of the Hallicrafter’s tube radios. The best ones have transformers and require 120 VAC, but this can be supplied by an inverter. After working on several models, I’ve now bought four of the S-40’s to refurb this winter on bad winter days. These will receive either upper and lower sidebands. I suggest buying the reference books on both the T-Os and the later tube Hallicrafters. The source mentioned above can supply a circuit diagram for most older radios.

The ‘creme de la creme’ is the Hallicrafters SX-71. This tube radio has a dual IF conversion circuit. That is, unlike most all other superheterodynes which have an IF frequency of 455 kHz, this one has a second IF conversion frequency that is considerably higher. Having two such IF frequencies vastly increases what is called “image rejection” and makes for a much more selective receiver. I’ve one of these I’ve refurbished. I wish I could find another one!

Now a warning about EMP and close by lightening strikes (which have similar effects as an EMP). I had a nice shortwave antenna with a gas discharge tube next to a Grundig Satellit 800. The gas discharge tube was supposed to shunt a fast moving voltage spike to ground. Yes, it was connected by 6 gauge copper wire to an 8 foot [deep] copper ground. Well now, we had a severe lightening strike which totally fried three circuit boards in the Grundig. A several hundred dollar lesson on Murphy’s Law.

To protect radios from EMP the recommendation I’ve found is this: wrap the radio in nonconductive plastic film. Then wrap completely with heavy duty aluminum foil. Then wrap in a 2nd layer of plastic film. Then add a second layer of aluminum foil. The “skin effect” for electrostatic charges tells us that multiple layers give better protection. If you can use copper foil, this is more conductive and better than aluminum. I’ve read conflicting opinions on whether or not it is best to ground the outer aluminum foil layer. My opinion is only to ground it IF the distance from the foil to the ground is very short. Else I read that the ground wire will simply act as an antenna and flood the foil with the voltage spike.

One might seriously consider a true uninteruptable power supply (UPS) for a tube radio for household use. Might well isolate it from EMP power line voltage spikes. Best Regards, – Les H.

JWR Replies: I’m also a fan of the older (pre-transistor) Zenith Trans-oceanics. I’ve owned four of them over the years, and still have two of them here at the Rawles Ranch. The radios of this generation are now five+ decades old, so I agree that replacing the capacitors is a must. (Otherwise you never know when one might go “bang” and make that distinctive “blown cap” smell.) When testing these radios (before re-capping them) it is best to use a Variac to bring the power up very gradually. Aside for buying a few spare tubes and perhaps a reel of extra tuning -dial string, they are relatively “bomb proof” and maintenance free. The book Zenith Trans-Oceanic: The Royalty of Radios provides some excellent details on how to restore these gems, as well as some fascinating history and price comparisons. By the way, Zenith Trans-oceanics are often available in eBay, including some that have already been “re-capped” and re-aligned. The scarce Pentagrid 1L6 tubes are also sometimes available on eBay, but it is best to be patient and wait for a “sleeper” auction to get one at a reasonable price. It is also worthwhile to look for inexpensive “junker” Zenith Trans-oceanics and AM-only Zenith “Universal Model” radios (with beat-up cases, cracked dials, and missing knobs), as a source for spare vacuum tubes and and telescopic antennas.