DCP-10 Direct Conversion Portable 10 Watt DSB/CW Transceiver|
This Portable Direct Conversion Tranceiver which I built called the DCP-10, was developed by a friend of mine in 1994. The design criteria was, low receiver current drain, medium transmitter output power, small-size and simplicity using a plug-in RF shelf (50MHz shown). The receiver board is a KK7B model R1, DSB Direct-Conversion receiver. For information regarding the R1 see;
I have worked many stations through out North America with the DSP10 on both CW and DSB. It is interesting that no one has ever noticed that I am using DSB instead of SSB. The DSB audio chain employs a simple compression circuit to prevent overdriving the final amplifier as well as a 3000 Hz low pass active filter. Here on the West Coast of Canada there is not a lot of activity on 6 meters so we were not concerned that using DSB will cause undue interference to other operators.
When working portable, I typically use my 2 element quad or 3 element yagi which are described on my Antenna Page. One of the mountain top sites that I operate portable from is very close to local TV and FM radio towers which put out a considerable amount of RF power close to 6 meters. I have found that the DSP-10 is not bothered by these near by RF sources whereas my FT-726R suffers greatly unless the antenna is pointed away from the TV towers.
You may wish to substitute a 2SC1972 transistor for the MRF262 output amplifier. The 2SC1972 is less expensive than a MRF262, and should still produce the same output power. Check RF Parts for availability.
The DSP10 is small and light enough that it can easily be carried in a back pack for extended hikes. Being the receiver draws so little current one can monitor the calling channels for many hours and not be concerned about running the batteries dry.
I use two crystals for the VXO and select the one I want with a miniture slide switch accessible under the top cover. The two cyrstals allow access to both the CW and Phone portions of 6 meters. (50.093 to 50.101 MHz for CW and 50.123 to 50.131 MHz for phone.) We have found the crystal osciallator to be unconditionally stable even when operating from mountain tops where it can be very cold in the winter or under a tent in the heat of a summer day. Unfortunately, stability and simplicity lead to a small tuning range which may be ok for portable/emergency situations.
There is something special about operating from a remote mountain top location with homebrew gear. No power line noise, computer birdies etc., all you hear is the quiet hiss of the receiver noise floor and maybe some distant thunder storm crashes until you tune across someone calling CQ. They just jump out at you above the receiver back ground noise when you tune across the band. An experience that amateur radio operators should have on a regular basis!
Specs: WxLxH = 100 x 150 x 50 mm
Modes: CW/DSB-SC, Sensitivity: 0.1 uV CW easy copy, 2000 uV max. input, DC: 25mA at 13.5V
RF Out CW: 10 Watts, (DSB-SC: 10 W PEP, 2.5W per SB) [1.6A at 13.5V], Spur Rad: RX -85 dBm, TX -90 dBc