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Radio Shack HTX-400
Factory Specs Modifications Extending Capabilities Links

          The Radio Shack HTX-400 is essentially the 70 cm twin to the 2 meter HTX-200. Rather than rehash everything I said about the HTX-200, I recommend you visit my page on the little 2 meter Radio Shack HT first. The two little radios are identical in appearance, and functionally similar. Like its twin, this radio puts out 200 mw on a pair of standard batteries, or a bit less using the 1.2 volt nicads. When using a 9 volt adapter (putting out at least 900 mAh), the unit puts out one watt. The photo below illustrates how similar the two units are in appearance. Except for the shorter antenna of the 400, the units are hard to tell apart.

        The 70 cm band is very near that of the FRS and GMRS radios, and thus the characteristics of the bands are similar. Most FRS radios are allowed to transmit at 500 mw, and thus put out more power than the 200mw of the HTX-400, so range is not great. A pair of these radios might be able to reach each other at a half mile or so; but even this is not certain. Hitting a repeater is possible at much greater distances, due to the much better antennas that most repeater sites have; but even here you are probably not talking more than 10 - 20 miles.

        Though UHF and VHF are both limited to line of site propagation, there are some differences. Line of sight is not truly line of sight, and radio energy tends to be able to look a bit farther than actual line of sight. UHF tends to be a bit less penetrating and has somewhat less range and ability to overcome terrain obstacles. As a general rule, lower frequencies can look just a bit farther over the horizon than higher frequencies.

        Because of the characteristics of the band, and the big head start that 2 meter had, 70 cm lags far behind in popularity, though it has gained a bit of a following. Still, the future of the band seems assured, if a bit less glamorous than that of 2 meter. The band is less popular than two meter, and has quite a bit more room. There are also some great radios out there, and recent developments make it easy to include the band on multi band radios.

        The size of the radio, so striking in the two meter HTX-200, is a bit less impressive in the 70 cm HTX-400. Little UHF radios are quite common, far more so than little VHF radios, particularly with the huge numbers of FRS/GMRS units being sold. Still, this is a handy little radio to put in your shirt pocket.

         Unlike the little GMRS/FRS radios, this unit can access thousands of frequencies, and is capable of a variety of repeater offsets, tones, and scanning modes. For its size and price it is a remarkable little thing. it can also take a full range of accessories, including an external antenna, power supply, and even an external speaker and microphone. A nearly identical model, set up for FRS, was made by Maycom for the now defunct Cherokee company.

        Radio Shack had originally been asking around $200 for these units; but eventually ended up clearing them out for about $50 each, as it eliminated its amateur radio gear from its product line. I was able to get the HTX-200 new, but missed out on a new HTX-400. I have been looking for one of these radios for years, ever since. I was eventually able to find one on the web for about $35. This is the low end of the price spectrum, but there is usually no problem finding one of these radios in the $50 range. Now they sit in my shack like a pair of twins - apparently identical, but with important differences.
    Frequency is selected in user configurable steps of 5, 10, 12.5, 15, 20, 25, 50 kHz, or 1 MHz, by use of simple up and down arrow buttons on the face of the unit. These may be cycled through manually, or scanned. Thirty memory locations are available for favorite frequencies. For repeater use, offset may be set from 0-8 mhz in 100khz steps. The unit is also capable of generating, and responding to a series of 47 subaudable continuous tones for repeater, call, or paging use.
    Standard convenience, and operation features include earphone and external microphone jacks, external power jack, back lit display, and key lock. During normal operation, the display itself shows the frequency, signal strength, status of the tone squelch, and offset, along with indicating transmit or receive function. It also displays a number of menus when the unit is being set up, and indicates the battery when the unit is first turned on.

     Like most of the modern little radios out these days, you really need the manual to do anything. Computer control means that many functions and memories can be contained in quite a small unit. All keys serve multiple functions, and each model of radio seems to speak its own language, which must be learned by the operator. Still, without such a system, it would be impossible to fit so many features into such a small radio. I found a little nine volt power adapter for this unit, and discovered the radio is so small that it can sit on top of the power adapter like a book on a shelf. I suppose this makes it the smallest base in the house (tied with the equally diminutive HTX-200), complete with scanning, memories, and full offset and tone. So what good is a one watt base with a tiny antenna?

    The only way to get any real use from these radios is by accessing repeaters. Standard offset (upon which the repeater receives, and the user transmits) for 70cm is generally 5 MHz above or below the transmit frequency. Repeaters for 70 cm are not nearly as common as those for 2 meter, but there numbers are slowly growing. Most urban areas have several. Even so, it is considerably harder to fill all of the 30 included memories of this unit, than the identical number of memories in its 2 meter sibling. I have listed the local repeaters in my home area below.

     Without a nearby repeater, 70cm does give the virtue of privacy. Between the limited range, and the huge number of frequencies available within the 30 MHz bandwidth,  there are always plenty of open frequencies available. This is the land of wide open spaces.


Repeater Transmit (user receive) Receive (user transmit) Tone Offset Location
Pewaukee 443.125+    448.125+    127.3 5 Mhz +  
Oconomowoc 442.025 447.025 + 127.3 5 Mhz +  
Delafield 444.125 449.125 + 127.3 5 Mhz +  
Menomonee Falls 444.425 449.425 + 127.3 5 Mhz +  
Milwaukee 442.650 447.650 + 127.3 5 Mhz +  



Frequency Receive 420 - 470 MHz
Transmit 420 - 450 MHz
Frequency Stability +/- 5ppm
Operating Temperature 14 to 131 degrees F (-10 to 55 degrees C)
Power Source DC 3.0V to 9V (at least 900 ma)
Modulation F3E
Impedance 50 Ohm
Dimensions 2-1/4 x 3-3/8 x 1-1/16 inches (85 x 58 x 26.5 mm)
Weight (without batteries) 4.2 oz (120 g)
Circuit Type Dual Conversion, Superheterodyne
IF Frequency (1st IF) 30.85 MHz
(2nd IF) 450 kHz
Sensitivity 0.22 uV for 12 dB SND
Selectivity 50 dB Min.
Spurious and Image Rejection: 60 dB Min
Intermodulation 60 dB Min
Distortion 10% Max.
S/N Ratio 40 dB Min.
Audio Output @ 10% THD 50 mW 16 Ohm, BTL
Power Output 200 mW, DC 3.0V/1W, DC 9.0V
Distortion 5%
Deviation +/- 5 kHz
S/N Ratio: 36 dB
Current Drain 600 mA

Mods, Tips, and Tricks

    There is not really much, in the way of modifications, which can be done to this little radio. There are a few tips and tricks though, including a very easy way to get extended transmit, and I have listed them below.

Radio Shack Manual for this radio eham reviews QST review.