HF all bands handheld transceiver for the radio amateur
by sv3ora

This page, presents a simple all HF bands transceiver for the radio amateur, designed to be a handheld device. Such a device is of great interest to the HAM community, but the commercial gear companies refuse to release such devices, even today, where they could be made very small. The best commercial handheld example that comes as close to it as possible, is the Kenwood TH-F6/F7 transceivers, that can demodulate HF DSB signals, but not transmit. Even such an expensive device does not have the selectivity to demodulate SSB but only DSB. There are some KITs (for example the TJ2B) that can also transmit on some of the HF bands as well, but these are big and bulky handhelds and they cost way too much as well. If you are lucky enough, you can also find some rare vintage handhelds (Mizuho), that could transmit in a few HF bands as well, but again they are rare and cost a fortune. Finally, if you are interested only on 12 meters and above, there are very few CB handhelds (for example the Magnum 1012 or the Albrecht AE-2990AFS) that can do SSB on these bands and guess what, they also cost a fortune.

For these reasons, I have decided to try to design a transceiver for the radio amateur, that would meet the next requirements:
However, there are quite a few compromizes that must be made, if these requirements are to be met. These compromizes will be explained as the aricle goes on, so let's start presenting one by one the transceiver components.

The power source

In any handheld transceiver, the choice of the battery is one of the most important things to consider, as many factors affect this choice, such as the size and the weight of the battery, the power that it can supply, the consumption of the transceiver, the charging capability, the cost of the battery and it's replacement, the ever-ready capability, the easiness of removing it from the transceiver etc.

The power source for the transceiver is chosen to be a composite 12v multi-cell AAA Ni-MH battery.
Several factors contributed to this decision. AAA battery cells are the most common cells after the AA and they can be found in almost every part of the civilized world, at the local stores. They are cheap (even the rechargable ones) and significantly smaller and lighter than the AA batteries. The weight and the size of the composite battery is not that good, compared to Li-ION and LI-PO, but I choose rechargable Ni-MH batteries because they can be recharged using any common cheap or expensive charger found also in most stores around the world and they are safer than the Ni-CD ones (which are abandoned in Europe anyway). An important advantage of the AAA size, is that when you are out and the batteries eventually discharge, you can immediatelly replace them with ordinary cheap non-rechargable AAA batteries, buying them at stores on the road and you don't have to wait for hours for the discharged batteries to charge. Initially, I did not know the exact power that the transceiver would consume, but I estimated that a 12v 950mA power source, would be sufficient for at least 1W of output power from the transceiver, while keeping it powered several hours during receive. A disadvantage of these batteries, is that they require battery holders (like many others), but I do not see a better way if they are to be removed easily from the transceiver.

I used solder type battery holders and I soldered them directly onto the PCB of the transceiver. If the holder clips are too loose, bend them a bit, so that they can keep the batteries firmly into their body.
This way, the whole construction is rigid and unaffected from vibrations as much as possible.

I connected the ten 1.2v batteries in series, to form a composite 12v battery. In fact, when these batteries are fully charged, the total output voltage will be 13v or more, which leaves a lot of headroom for discharging. I did not want to use any kind of internal charger, because these chargers tend to be noisy, which would possibly affect the operation of the RF circuit. Not only that, but by having the external mains-powered power source connected to the transceiver while listenning, it's almost certain that noise will be induced into the circuit.

The choice of the rechargable battery type, is also important. Most common Ni-MH batteries, have high self-discharge. This means that when you leave the batteries for a long time into the transceiver, even if these are initially fully charged and the transceiver set to the off position, they will be discharged by themselves. Practically, this means that when you need to use your transceiver
the most, it will be discharged. It happens all the time to me and it will possibly happen to you as well. The solution, is to buy low self discharge Ni-MH rechargable batteries. Don't go for the most expensive brands if you can't afford them. Chinese brands, like the ones I have used, are as cheap as high self discharge types. It is not always obvious if a rechargable Ni-MH is of low self discharge type. The easiest way to find this out, is to look at the battery case, when you buy them new. If the case has the instruction, that the new battery has to be charged before use, then it is a high self discharge type. If it says, "ready to use" or something similar, then it is a low self discharge type, so go for it.

The frequency counter

The frequency counter is a useful addition to this non-DDS transceiver. The transceiver is a direct conversion one, so the frequency counter input, is directly connected to the local oscillator, to display the frequency the transceiver is tuned to. I could use a classic 2x16 LCD based frequency counter, but this would be way too big and heavy for this transceiver. So I have chosen one that used 7-segment displays, which can be found in small sizes. Below is the schematic of the frequency counter.


pic 16f628



898 -3- r1k

qdsp -6064

14 06 01 16 12


07 02 15 11

27k 03 08 03 14 02

input bf199

330r 100nf

09 04 13 08

05 10 05 12 05

11 06 11 03


04 12 07 10 09


13 08
09 07

15 01





16 17



The Schematix data for this schematic, is shown below. You can use this data, to send this schematic to your friends through radio.

al5v bbic1 bdpic be16f628 bk100nf blsi bnic1 bqic2 btic3 cbic2 cd898 cethree cfr1k cjrf ckte clhe cmea cngn coea cpea cqgn crea csea ctgn dbic3 ddqdsp de6064 dlae dm14 dnwh do06 dp01 dqwh dr16 ds12 dtwh ek560r eles enwh eoea epea eqwh erea esea etwh flae fnwh fo07 fp02 fqwh fr15 fs11 ftwh gkit glhe gmea gnwh goea gpea gqwh grea gsea gtwh hj27k hkes hlae hm03 hnwh ho08 hp03 hqwh hr14 hs02 htwh iginput ihts iieh ijte iken ilne imbf199 inwh ioea ipea iqwh irea isea itwh ji330r jj100nf jlae jnwh jo09 jp04 jqwh jr13 js08 jtwh klie kmea knwh koea kpea kqwh krea ksea ktwh llee lm05 lnwh lo10 lp05 lqwh lr12 ls05 ltwh mnwh moea mpea mqwh mrea msea mtwh nl10k nnwh no11 np06 nqwh nr11 ns03 ntwh oj5v okts oleh omea onwh ooea opea oqwh orea osea otwh pm04 pnwh po12 pp07 pqwh pr10 ps09 ptwh qnwh qoea qpea qqtc qrea qsea qtwh rk22pf rnwh ro13 rp08 rr09 rs07 rtwh sjrf skte slei smea snwh soea spea sqea srea ssea stwh tlae tm15 tnwh to01 ts04 ttwh uk4mhz uler unwh uoea upea uqea urea usea utwh vlae vnwh vo02 vs01 vtwh wjrf wkte wlen wmea wnwh woea wpea wqea wrea wsea wtwh xk22pf xm16 xnwh xo17 xs10 xtwh yntc yoea ypea yqea yrea ysea yttc zo18 zs06

The 7-segment display used, is the vintage HP QDSP-6064 that contains four digits, connected internally for common cathode multiplex operation. It is in DIP package and it is really the smallest 7-segment display I am aware of. If you cannot find this display, no problem, replace with any other common cathode 7-segment display, but try to find one that is small, so that it can fit into your handheld.

I had one 898-3-R1K resistor network available and I needed exactly eight resistors for limiting the current to the display, so I used this one. This has eight isolated resistors inside, like shown in the schematic below. However, if you cannot find one, you can use eight discrete resistors instead.

The frequency counter, including the display, is tiny and lightweight. It also has auto-range. However, with a four digit display, the resolution is limited to 1KHz for frequencies below 10MHz and to 10KHz for frequencies above that. This is the counter resolution, not the tuning step of the transceiver, which is designed to be analogue anyway (no DDS). 1KHz is ok for a portable rig, but 10KHz is not too good. However, even with this limitation, the frequency counter is still a very useful addition and besides, it is very small.

The HEX file for programming the microcontroller for the frequency counter, is presented here. It can be either downloaded as a file from this link, or coppied from the listing below and pasted into notepad and then saved as a file with a .hex extension, for loading into your burner program.


to be continued...

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