Refinement of the smooth range generator. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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Mechanical part

In my opinion, the vernier mechanism of the transceiver is unsuccessful - there is no possibility of fast frequency tuning. I propose to install a vernier from the R-311 radio receiver, without changing anything in the fastening of the GPA unit itself. To do this, the diameters of the disks (3), rollers (10) and axle (16) will need to be made equal to each other, say, 24 mm. I propose, for example, to put a disk with a diameter of 16 mm on the axis (24), make the disk (3) 24 mm in diameter, and the roller (10) remains the same - 24 mm. The transfer ratio will be 1:1. The double vernier knob will provide both quick and smooth tuning of the transceiver.

Improving the thermal stability of the GPA

To increase the frequency stability of the GPA, I propose to assemble it by surface mounting on ceramic racks. Contactless KPB (butterfly) is made of brass, and not of duralumin, which has a noticeably worse TKB.

It is desirable to exclude the varicap from the smooth tuning of the GPA and apply the detuning scheme given earlier in "Radio Design" No. 1-98 p.32.

GPA division factor

On the HF bands, you should change the division factor in the DPCD frequency divider circuit so that Fgpd is always higher than the frequency of the received signal by the value of the intermediate frequency Fpch. Input bandpass filters do not provide sufficient attenuation of the image channel at receive frequencies below 10 MHz. This is especially noticeable in the evening on the 3,5 and 21 MHz bands. Accordingly, the switching of USB and LSB modes changes places - switching of relay K2 in block A4 - FCZCH (see the book RA3AO "Amateur KB transceivers" or magazines "Radio").

For ease of use, below is a table of values ​​for the frequencies of the GPA, DPKD and the division factor on all HF bands for the intermediate frequency Fpch \u8d XNUMX MHz.

Due to the decrease in the division factor in the DPKD, there will be no noticeable deterioration in the dynamics

DD3(dB) = GPA noise - 10 lgV, where

B is the passband of the quartz filter.

DD3 = 138 - 34 = 104 dB. (In this regard, RV4LK concludes that it is not necessary to reduce VFO noise using division, RW3AY)

Author: A.Kuzmenko, RV4LK, Ulyanovsk; Publication: N. Bolshakov, rf.atnn.ru

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