Note: As always with my articles you can click on any image to view a much larger resolution version.

      When I first realized there was this thing called radio, my first receiver (after the ubiquitous crystal radio) was a Hammarlund HQ-100. It was given to me by a neighbour when I was about 12 years old in 1973. It was fairly beat-up, scratched and dented, but it worked. I sat there for years listening in on all the chatter and broadcast stations from around the world, fascinated by the idea that radio can travel around the globe to my bedroom.

     Since then I have always had a soft spot for the HQ series of Hammarlund receivers. I always seem to have to some example sitting in my shack. Of course in the boatanchor arena of receivers, it may not be the most stellar performer, but like I said, I have a soft spot for these radios. I tend to stick with 100 or 110 series.

     I recently acquired the rarest of these, the HQ-110AC-VHF. This final variant of the 110 series not only includes the 6m band but also includes the 2m band as well. Information about these particular models on the web is slim at best, however what I have found is this one was from the period when Giannini Scientific owned Hammarlund. This variant was the last HQ-100 series tube receiver built by the company. This article, while not a detailed restoration article, will cover the finished restoration to show some of the unique features this variant contains.

     The HQ-110 series of receivers was designed for Amateur Radio use, so it is not a general coverage receiver like the HQ-100 series. The HQ-110 is a dual-conversion superheterodyne receiver which tunes the basic amateur bands: 1.8-2, 3.5-4, 7-7.3, 14-14.4, 21-21.6, 28-30 and 50-54 MHz. Features include: antenna trimmer, analog dial, noise limiter, RF gain (labeled sensitivity), S-meter, Selectivity BFO with frequency tuning, CW tune and AVC on/off. This radio does not have a built-in speaker. The receiver incorporates a linear detector which provides for the reception of SSB and CW signals, in addition to the standard AM product detector. There are 3.2 ohm speaker terminals on the rear panel. The suggested optional speaker is the S-100. There is a tube chart printed on the rear panel. It measures 16.25 x 9.5 x 9.2 inches and weighs in at ~30 lbs (depending on variant).

The HQ-110 was superseded by the imporved HQ-110A. There are at least two major variants of the HQ-110A: One with a small metal tag that says HQ-110A between the two scales and the raised cast Hammarlund logo; and another which has a metal tag on the front with "VHF" (missing on mine, more on that later) and below a silkscreen with "HAMMARLUND HQ 110 A". This model has a pre-amp on 2 & 6 meters. From information I could find, I believe it is the last of the series.

     The HQ-110 was produced in at least 3 serial number ranges. The first run includes serial numbers up to 4199; the second run includes serial numbers from 5000 to 7000; and the final run includes serial numbers above 7000. The serial number can be found stamped into the rear apron of the chassis.

     The major changes in the second serial run are in the area of V1 and V2 and in the BFO circuit. The coupling arrangement between T1 and T2 was modified significantly, as were parts of the second mixer circuit. The second mixer crystal was changed from a 3.49 Mc to 2.58 Mc. Also, there were finally some further attempts at temperature compensation to help to reduce the inherent drift of the receiver. In addition, the BFO circuit was changed considerably so that its output comes from the plate rather than from the cathode as previously done.

     In the third serial run, there were further changes in the T1/T2 coupling as well as new changes in the RF stage and the second mixer. Most notably, the Antenna coils are no longer gang-tuned to the mixer and local oscillator. The antenna coils are now resonated by the antenna trimmer only, leaving the main tuning capacitor a 2-section variable, rather than a 3-section as it was previously.

     According to a Product Addendum covering the second and third runs, 6 capacitors were added to improve stability in the high frequency oscillator and BFO sections; 2 coils were added to the second mixer and local oscillator to improve stability; and a resistor across the output transformer was added to provide an emergency speaker load.

     The HQ-110AC-VHF was the variant of this receiver that included all of the optional features. Of course it includes the clock. However most notable is the incorporation of the 6m preamplifier/2m converter module. Below is an image of my restored HQ-110AC-VHF with the cover off showing the 6m preamplifier/2m converter module nestled between the RF and IF cans.

     The module functions as both a 6m pre-amplifier and a converter for 2m reception when the proper controls are selected. On 6m the performance is significantly improved over previous variants by the use of this pre-amplifier, giving 6m performance the same sensitivity as on the lower bands. A huge improvement! This improvement is accomplished by the use of a 6CW4 Nuvistor pre-amplifier stage.

     In operation, to receive 6m signals, the bandswitch is turned to the 50 to 54 MHz position and the volume control is pushed in. A separate 6m antenna must be connected to the appropriate phono jack on the rear. The normal 6m antenna connection on the barrier strip is not internally connected and only the RCA jack below the barrier strip is used. For 2m reception all one has to do is pull the volume control out, again having a separate 2m antenna connected to the RCA jack located on the far left. Pulling out the volume knob engages a relay in the module which provides power to the converter circuit; which coverts the 2m signals to 6m. The converter consists of four 6CW4 Nuvistor tubes in a combination 2m converter/6m pre-amplifier circuit. I will include a PDF document of this module at the end of this article, if you are curious about the circuit and its installation in the HQ-110A. It can also be used in the HQ-170A as well.

     Here are some detailed images of the pre-amplifier/converter module, front and back:

     One of the interesting details of this variant is the factory removal of the 5U4 rectifier tube and the addition of solid-state rectifier. Diodes were added to a small barrier strip, and a jumper/resistor network plug is incorporated into the former rectifier tube socket. The plug incorporates some resistors to keep the voltages the same as the tube rectifier supplies, and afford some level of current limiting when the power is turned on. Here's a close-up of the jumper/resistor plug added at the factory:

     Additionally, dipped mica capacitors are used in all the transformer cans, which eliminates the so-called "silver mica disease" so prevalent in these radios. This modification was first introduced in most "A" series Hammarlund receivers. This also helped improve stability overall in the radio, particularly in the RF section.

     As you can see in the images, this radio is in what I like to call "near-new" condition. Careful attention was placed on restoring the chassis without removing any of the original cadmium plating. Most people take wire brushes or Scotchbrite pads to their chassis. However there are much better chemical solutions available to remove cadmium and aluminium oxides from chassis which are much less invasive or destructive. The trick, of course, is to get a chassis that has not experienced this destructive "restoration" approach during its lifetime. Once this plating is removed or even slightly scratched, as is the case with using Scotchbrite, the only alternative is replating of the cadmium; something that is more costly then this radio is worth. I should also remind anyone out there thinking of scrubbing away at the plating, cadmium is very carcinogenic and poisonous effecting neural tissue of the brain once liberated; especially in the young and elderly. It also permeates everything in your house and is nearly impossible to fully remediate. It's worse than mercury in those regards.

     The only modification I performed was the addition of X1/Y1 safety caps, along with line chokes on the line input and changed to a three-prong grounded AC cord. On this radio it significantly improved the noise floor; by about 4 S-units in my location. It also of course improved safety and removed that "AC tingle" when touching the cabinet.

     Of course, I performed the usual testing and replacement of all out of spec parts, which did include a few mica and ceramic caps and a few resistors. I also replaced all the resistors in the oscillator to 1% tolerance mil-spec carbon composition; which helps improve stability and reduce drift. Also replacement of the all the electrolytic capacitors to the same values as the original. Finally a careful alignment per the manual was performed, with some special offset tweaks to the IF sections which improve audio quality.

     One of the things that always frustrates me is the loss of certain cosmetic elements. On many of these Hammarlunds small badges are glued to the front panel which either call out the model, or in this case, says the word "VHF". On this one that badge is normally centered above the silk-screened Hammardlund logo. These are basically "unobtanium" since very few of these VHF badges were manufactured in the first place; even if you include the HQ-170A-VHF. The numbers are in the fifties. And very few survived to this day. The solution is to scavenge the plate from on old junker HQ-110 I have. On it it says "HQ 110" with the Hammarlund logo in the middle. So I am going to take this badge and put it on a belt sander and remove the "HQ 110" silkscreen and smooth out the surface and edges. I will duplicate the "VHF" tag in Photoshop and create a 1:1 scale water-transfer decal on my printer. I will apply it to the sanded badge, spray some clearcoat over it and glue the badge in the correct spot on this receiver. Done!

     Here's an image of the badge on another receiver. In this case a HQ-170A-VHF owend by another Ham:

     Overall the performance of this receiver is the best of any HQ-1xx series receiver I have ever owned. The radio has very consistant sensitivity across all the bands. The performance on 6m and 2m is spot on. I do operate AM on 6m and 2m, which is fairly active in the New York City area where I live, and this receiver has blended into that operation perfectly. It's SSB performance is totally accpetable as well, since it is inherantly more stable than previous variants; along with the tighter tolerance components I added to the oscillator. It even manages fairly good performance tuning in FM by using a slope tuning approach.

Many people malign these receivers mostly because they lack the knowledge of how to use them properly. SSB reception is fine; if you understand that you must use the sesitivity knob for volume, and the Q-multiplier and CW tune all together to proeprly detect a SSB signal with no distortion. If you know how to use it properly, this little receiver can do it all.

Before I end this, here's a few more images of the restored HQ-110A-VHF

     Here's the PDF for the 6m pre-amplifier/2m converter module: Click here