Manual zz. The use of this information may void your radios warranty, The modification of your radio may make its use illegal. The owners of this page DO NOT warranty any of this information, nor accept any responsibility of how you use its content. You may be able to peel the epoxy right off to expose the pins of the IC. If it is not soft enough to peel off, you can use a W hair dryer to heat the epoxy enough to remove it.
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Disclaimer: As a licenced amateur radio operator, I am publishing this information for the use and benefit of the ham community. If you are an Meter 'freebander' and are reading this page, I strongly encourage you to become a licenced ham and cease illegal operations on 11 Meters. If you write me with a question about modifying your radio or where to buy an amplifier, without providing a verifiable ham callsign, I will not answer your email; furthermore, your email will be forwarded directly to the Federal Communications Commission, or to the radio regulatory agency of your country.
I do not support or encourage any sort of illegal 11 Meter operations. They are probably among the most modified, as well. On this page I will detail the results of some of my tinkering with these rigs. It is not my intention to cover ground that has already been covered by others; there are many fine resources on the web describing various mods and enhancements to these rigs.
What will be covered here is information that I have found through my own experiments that I have not seen covered elsewhere, as well as my own opinions on some of the other published mods. More obscure notes from KM6ZQ. But how can this be? When I finally managed to acquire an HTX last year, I decided to investigate to try and prove or disprove this notion once and for all.
Examination of the schematics for both radios showed that the RF sections were indeed almost identical. I reasoned that the , being an 'allmode' radio with AM included, may use the common CB radio design practice of having a wider 'compromise' IF crystal filter to improve the RX audio response on AM.
The center frequency of both filters is Sure enough, the USB carrier oscillator frequency is different in the two radios!
Shown below is a chart of the carrier oscillator frequencies for both rigs, with a LSB value extrapolated for the HTX As can be seen from the graph, the HTX filter is indeed significantly narrower than the filter.
The next question becomes 'Can an HTX filter be transplanted into a for better performance? Be sure to give them the HTX catalog number, , as well. The only downside to this mod will be that, since the frequency offsets for the display readout are controlled by fixed values in the CPU microcode, your frequency display will be off by 1 KHz in both USB and LSB modes. The Chipswitch replacement CPU will not compensate for this either, and the people at Chipswitch haven't shown any interest in releasing a new version to allow for this mod.
I did not concern myself with fixing LSB, since If you operate quite a bit of AM, you will notice that AM signals do sound more muffled with the narrower filter. This is normal, and can be compensated for somewhat by off-tuning the signal a little with the RIT or the main dial.
If you operate a lot of AM, however, this mod may not be for you. I always thought the RX audio on the sounded a little wimpy, even with an external speaker.
Rogerbird has a good mod on his web site to increase the overall gain of the audio stages, but I didn't think this was my problem. A sweep test of the audio chain from the collector of Q to the speaker showed an overall response of about Hz to Hz.
OK on the high end, but a little restricted on the low end. I paralleled C and C each with a high-quality computer grade.
Return to Top. There are lots of good descriptions of mods floating around to enable the RIT to function on transmit, so I won't re-invent the wheel here. Rogerbird has several listed on his page.
The only thing that I can add is that I placed a short across diode D when I did my mod. It isn't needed any more once the RIT is enabled for transmit, and may introduce some non linearity on the low end.
These adjustments control the frequency of your carrier oscillators, and will knock your audio out of whack if not adjusted to spec. Use the instructions in Mod 3 or Mod 4, they are correct. I always wondered why, when we have a radio that tunes in Hz increments on the main dial, everyone seems fascinated with having KHz of 'slide' on the RIT control.
Seems kind of silly. My preference was to reduce the range of the RIT circuit by placing a 22 K resistor in series with the high end of the RIT pot and a 10 K resistor in series with the low end.
This reduces the overall tuning range of the RIT quite a bit, and makes fine tuning a lot less touchy. You can see this mod in my schematic of the RIT shifter for the crystal filter mod.
It's just personal preference on my part, but that tiny knob doesn't make a real great VFO. Did you ever wonder what those 2 extra adjustment pots on the synthesizer board are? To adjust them, you need a good scope with at least 60 MHz bandwidth MHz would be better. Preset the rig to 29 MHz. Connect the scope to TP, and adjust VR for the cleanest sine wave. Repeat using TP and VR That's all there is to it!
Anyone who has opened a has noticed the melted plastic of the LCD holder around the display lamp. This seems to have been a major design screwup on Uniden's part.
My solution to the problem was to drill several small holes in the top and sides of the LCD holder for cooling. I then removed the stock lamp and suspended a pair of 12v micro-lamps from Radio Shack through two of the holes in the top.
Since I never liked the ugly amber color that Uniden chose for the backlight, I topped it off by making a red filter to fit behind the LCD unit from a red Rolodex plastic card protector item , available in a pack of 5 colors from your friendly office supply store.
Note: the blue ones work nice in vintage Drake gear. Inserting the red filter requires careful disassembly of the LCD holder, so don't try this if you are all thumbs! The result is a pleasing, evenly lit red display that is easily visible under most lighting conditions.
Even if you don't go the full route and install new lamps with a different color filter, the cooling holes in the LCD holder are probably a good idea. This is where I get to express my opinion of some of the other mods floating around out there. Constructive comments are welcome; flames will be ignored. Don't do it. My had this mod in it when I got it. It just so happened that I lived two blocks from a grain elevator at the time, and the truckers waiting to offload their grain liked to sit on CB and yak.
Any time one of them would transmit, the entire band range of the would be blanketed with white noise. This was caused by the use of switching diodes across the IF crystal filter in this mod. Under strong signal conditions, these diodes began to break down and effectively killed the selectivity of the radio.
If you want repeater splits, get a Chipswitch. It's a much better solution. Highly recommended. What more can I say? You get memories, repeater splits, and 12 Meters too! I bought mine from the friendly folks at Bill's 2-way. Bill Nadzam was very patient in working with me on a problem that it turned out was of my own creation. You can't go wrong with these folks. Another don't, if you respect your fellow hams. That extra couple of watts will never make it to the guy on the other end, but it will sure tick off your neighbors.
This effect will be mitigated somewhat in the HR due to the fact the the transmitter uses low-level modulation for AM and the signal is bandpass filtered by the IF crystal filter, as opposed to the classic high-level modulation that is used in older AM transmitters, but the result is still not good.
A scope is also the best way to set the ALC. Probably not worth it, especially with the solid-state amps that are out there on the market. An old rule-of-thumb is that it takes about 6 dB to make an S-Unit. A 3 dB increase in power is a doubling of power output.
So if you double your output, you will see half an S-unit on the other end. An increase of 5 or 10 watts just isn't enough to notice under most conditions. If you get an external amplifier, just make sure you get one that is actually linear; many of the cheaper so-called 'linear amplifiers' operate in a class-C mode with no bias, and splatter the band horribly when used for SSB or AM. The worst offenders seem to be the ones that resemble a cigarette carton with a heatsink on the bottom; avoid these like the plague.
Sometimes the only way to know for sure is to physically check: take the cover off and apply power to the unit; pull the TR relay manually by grounding the collector of the keying transistor, and check with a voltmeter for. Click HERE for a good explanation of power amplifier classes of operation; this description discusses tube amplifiers, but the concepts are the same for solid-state amplifiers.
My philosophy is that unless you have been to engineering school and have access to CAD equipment and network analyzers, don't dink with the RF strip. The engineers that designed the thing probably have more education and resources to do the job right than you or I.
Be careful how high you set the AM power, also. There is only so much 'headroom' in the transmitter strip, and too much AM power will cause signal clipping and distortion. Don't rely on a modulation meter, the only way to see what is really going on is to monitor the RF output with a scope. I'm currently investigating a more readily available part for this mod.
It seems worthwhile, but I'm not sure what the point of removing D is; this diode provides AGC control to the front end, and would seem to leave the radio more susceptible to front end overload if removed. I plan on leaving it in.
Doc's Radio Repair Repair and Mods for lots of interesting rigs.
PRESIDENT HR2510 Owner's Manual
Press the Span button until the type of radio you have is displayed on the readout. Then press the Band button to enter that selection into the microcomputer's memory. If your radio is turned off for an extended period of time, or if a severe electrical disturbance sparking wires, shorts, etc. Is caused on the power supply to the radio, the internal memory inside the microcomputer chip may 'forget' what you have programmed into it. If this should happen, your radio will display ' HR ' and you will need to re-program it just as you did when the chip was first installed. Also, a severe electrical disturbance may cause your radio's memory to become 'confused', causing improper frequencies or strange character to be displayed on the readout.