Topband: Home made Top Band receiver.

[scaroni]

Hi to all the Topbanders,

after reading about the receiver dynamic range, and the problem generated by
the PLL or DDS oscillators in term of not good phase noise, i would try to
made a single band 160 high performance cw receiver.
I have here in the shack an IC 775, IC 737, Drake R4T4, and i am intrigued
to check the performance of this receiver compared to an H.M realizazion.
Looking around, the best thing to do on 160 seems to be a single conversion
like KV4FZ also agree in his message, so step by step my doubt about this
realization, from antenna to BF:
1) put a low Q bandpass filter, low loss abt 1 or 2 dB
2) put a xtal filter made here by  an OM friend, BW  about 25 Khz - 3 db,
from 1820 to 1840, loss abt. 7 db, i have one on this unit before my
receiver now and all the 9+50 signal on AM band was really deleted! is
really like a knife.
3) first problem, the mixer, shure must to be double balanced like the SRA3H
Mini Circuit(more than 23 dBm of OL), but i have read about the high
performance mixer made with the Siliconix SD5000 like the project of G3SBI,
or the Siliconix 8901 like used by N6NWP, the higher IP3 like +46 dBm input
in 160 is for the SD5000, and the power of OL is lower than required with
the double balanced diode mixer.
So wich will be the best???
4) the OL of the first conversion will convert near to 9 MHZ IF the signal
from 160, so looking for the best phase noise, or low noise, i'll tempted to
use a VXO, or a VFO, someone have some good idea for the best oscillator
with no more of 20 KHZ of BW??
5) after the conversion i would use  a post mixer amplifier like made by
N6NWP, using Motorolola bipolars MFR 586, or G3SBI version MFR580A, this
last have an IP3 output of +56dBm!!!
Now a narrow band 250 or 125 Hz Xtal filter, followed by another amplifier
and another narrow filter, to improve the selectivity
6) BFO and the mixer for rivelator(now one with not so high IP3 may work
also well) + AF stage
7) the agc made only in AF stage if is possible, or changing the gain after
the first filter in the amplifier between the two IF filters.

So, i believe that a single band receiver like that explained must to beat
all the amateur receivers, so i'll happy if is possible to have some
information, or suggestion for this realization.
If there are some schematic diagram about all the block above explained.
All the block will be made in single box, with 50 ohm input/output, to
reduce not desired mixing or spurius signal, connected with BNC or SMA
connector.
The idea is starts after reading the following:
Numbers of Radio Rivista, our OM Italian magazine
Seventh edition of "Radio Comunication Handbook" by RSGB
So Topbanders, I'm waiting your info!!!

VY 73 and see you on Top Band.

Giulio IK2DED.



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