G8AEV 2 Metre Converter Mk2

G8AEV 2 Metre Converter Mk2

A VHF 144MHz in, 28MHz and others out

 

This Transistor Tuner/Converter described below was a good and cheap way to listen to the 2mt band back in the late1960’s early 70’s  

Designed by the late John Hartley, G8AEV who passed over October 2005, it’s a very good design with only a few sprog’s and what there present are of a low level and even by today’s standards its sensitive and well ahead of its time using FETs for a quite a low noise output.

Back then most Amateurs operated on the HF Bands, with Top band (160Mts - 1.8 to 2.0 MHz) being used as 2 Metres is today as the local chat Band,  so all Hams had an HF receiver .

The cheap way to receive 2 metres was to connect a 2mt in,  HF out,  converter to the Ariel input  to your shacks HF receiver and listen away

2mt AM, and FM (using slope demodulation) could be resolved and also SSB to, if your HF receiver had a BFO,  AM was the norm back then as few Hams had SSB equipment.

The Manual  G8AEV 2 Metre Converter

 Page 1,

 Page 2 including the circuit

 Page 3

Page 4

 Note 

TV manufacturers in the late 60’s were in the changeover from Valve (tube)  front ends in their TV receivers to the new RF Bipolar transistors  which were still in their infancy,  so the use of  40604 duel gate Fet with a 100 MHz conversion gain of 23 dB typ,  was indeed revolutionary

 

 

Source:- My own collection
Donated by a very good  friend, now sadly silent key G0DQO Bill  

Practical Wireless August 1964, Transistor Tuner/Converter

 Practical Wireless Transistor Tuner/Converter

 

The Transistor Tuner/Converter described in the August 1964 issue was a one, two or up to five transistor frequency converter

It was in effect the front end of a normal radio set, with a traditional Denco Blue coil front end RF tuned circuit , tuned by VC1 

This fed a to the Base of the first OC171 (Tr1) and amplified and the signal appeared at the collector

and tuned again the the Denco Yellow coil with VC2

the output of this yellow coil is fed to base of the next OC171 (Tr2)

If you note Tr2 is also wired with a third Denco coil this time a white oscillator wired in a Self oscillating mixer circuit

Here's a clue, instead if changing the base current to make the transistor oscillate, The Output from the collector is fed back to the emitter to change that 

This mixer oscillator OC171 (Tr2) runs at 1.6 Mhz and the base of this transistor is fed with the received signal the frequency the converter is tuned to, the two mix and hey presto the out put appears

this can be fed directly to a Medium wave radio tuned to the converters output

As with all mixers a number of other mix frequencies appear at the out put car has to be used to tune the Medium wave radio to the correct one 

One set back of this set is the coils fitted were 3T range about 1.6Mhz to 5.5Mhz to cover the Long wave all the way to 10 mtrs the builder needed to purchase 5 ranges of coils and it cost a lot of money.

N.B

Denco made two types of Oscillator a White 1.6Mhs +- and Red 465Khz to run with each coil set

except there was no specifically made 1.6 Mhz Osc coil for the lower 1T range 

Denco made a range of IF transformers again for 1.6Mhs +- and 465Khz 

yes after changing a OC171 (leaky ) to a spare AF116 I had it works well 

now part of my collection

Practical Wireless November 1960, Pocket Superhet

Practical Wireless Pocket Superhet 

The PW Pocket Superhet described in the November 1960 issue was a 6 transistor and 1 diode pocket transistor radio designed for medium and long wave reception

Using germanium transistors through out, the OC44 in the front end was really pushing the technology with a

Transition frequency (ft),  8 MHz: 

a Forward current transfer ratio (hFE), min: 100

Maximum collector-emitter voltage (Uce), V= 12

as usual for the time period one slight mistake and the device was ruined and at 28/- each, that's 28 shillings or £1.40 in decimal currency, which would equal £28 each in today's money, so failure of a device would be a financial disaster.

Click here to see how poor the GB £'s value actually is now

Measuring Worth

Semi conductor line up

OC44 RF & Oscillator/mixer

OC45 1^st IF

OC45 2^nd IF

OA81 Demodulator & AGC

OC71 Audio driver

2 x OC72 Push pull Audio O/P

                                                                Power = PP4  9volt battery

                                                             Speaker 2 1/2" Celestion 3 ohm

I regularly use this site for Transistor Data

All Transistors

I am fairly lucky my dad sent off to Practical wireless for the case, seen here

and started buying the parts each week what actually happened is lost in time

but he never made it.

I have been left a mint case and a Circuit diagram supplied by an old friend

who's dad did make his 

                                                                     The Blue Print

I have all the parts to build mine

the Question now is

Shall I

Taylor 45c Valve Tester

Taylor Valve Tester 

My main Valve(tube) tester

and very reliable

So simple to use, but you must be aware that there are a number of versions

and some valve(tube) data listed is WRONG

find a copy of the amendments

When it arrived it had slight wear in the “Test Selector “ switch but with a bit of switch cleaner and electrolube contact grease it works fine and I can put up with a bit of mechanical wobble

This can test all types of normal valves , Diodes , Triodes , Pentodes, Tetrodes, indirect or directly heated.

Tests:

Inter electrode leakage/shorts

Mutual conductance

Plot Ia/Vg at a range of parameters

Fully functional and used regularly

Source:- My own collection
Donated by the son of a deceased colleague

AVO Characteristic Meter Mark lll

AVO Valve Tester Mk 3

 

My Reserve Valve(tube) tester

When it arrived its meter was stuck on the end stop

and the overload kept buzzing and tripping out

a little bit of circuit work and a considerable amount of work on the meter

brought the beast back to life

This can test all types of normal valves , Diodes , Triodes , Pentodes, Tetrodes, indirect or directly heated.

Tests:

Inter electrode leakage/shorts

Mutual conductance

Plot Ia/Vg at a range of parameters

Fully functional but little used

Source:- My own collection
Donated by the son of a deceased colleague

AM Amateur Radio wanted

HF, AM Amateur Radio wanted 

for my personal use

Have you a

KW Vanguard
KW 160

Heathkit DX 60

Panda Cub

Heathkit DX 100

or any HF AM transmitter for sale ?

is it a failed project or perhaps you have one rotting in a shed ?

Leave me an e-mail address

in the comments box below
(click on no comment) 

and I will get back to you

UK only thanks

AVO Valve Characteristic Meter Mark IV

AVO Valve Tester Mk 4

My Main Valve(tube) tester , It been a good old friend for a number of years

It was missing its Vset ~ knob when I had it and 

years later I have never needed to adjust the V set ~

This can test all types of normal valves , Diodes , Triodes , Pentodes, Tetrodes, indirect or directly heated.

Tests:

Inter electrode leakage/shorts

Mutual conductance

Plot Ia/Vg at a range of parameters

this machine is an excellent compliment to any workshop

Lafayette HA55A, Air band Receiver

                                                                     Lafayette HA55A

A 1960’s Air band receiver

This was one of my few encounters with a Nuvistor 6CW4 in the front end

The set now works however I have noted a few issues with regards to its original specification

Tuning range 108 –136 Mhz

See below

Sensitivity 4uV

Even with a Nuvistor the 4uV is quite poor

Image ratio 40dB

Actually the set suffers from poor image rejection and one can receive a range of Band 2 Broadcast stations which can swamp the receiver

The set does use a strange selection of valves even for the 1960’s,

Apart from the above negatives the radio receives Birmingham very well

HA55A Circuit Schematic 

HA55A Alignment 

Hope this helps

 

KW Radio On Air Event

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KW 76 ,KW Atlanta, KW 204, KW Valiant, KW Viceroy, KW201, KW Vespa, KW2000, KW2000A KW2000B

Get It on the Air

KW Weekend 5^th- 6^th January 2014

 

This is one of my collection a KW2000's acquired in the late 1990's in a very sad state .

All the Hunts have been changed, the PSU electrolytic's have also gone and a few resistors changed

then a full realignment 

I never fully addressed the aesthetics, as the tuning escutcheon plate is from a 2000a

and I never quite got around to changing the 1/4” Microphone jack socket back to a DIN

The mechanical Filter did not require any work at all

A superb radio of British manufacture from the early 1960's giving excellent audio