RF Coils - Stabqoil SQ & Qoilmax QM
All photos copyright John Mills, last updated 28 Dec 2009
The "STABQOIL" (registered trade mark, British & Foreign Patents) is a unique design of
coil with a built-in adjustable capacity trimmer. It is temperature compensated and has
very high "Q" values. "QOILMAX" are identical to "STABQOILS", but WITHOUT the built-
in capacity trimmer. The standard range of "STABQOILS" for Broadcast bands are fitted
with negative temperature-coefficient 10/40 pF trimmers and cover 150 Kc/s to 32.0 Mc/s
(2000-9.5m) in 5 wave bands (plus a sixth general only coverage S.W. band) Four
complete ranges are available as follows:
For 460 Kc/s I.F's, 1 range using 500 pF gangs and 1 range for 320 pF gangs
For 1.620 Mc/s I.F's, 1 range using 320 pF gangs and 1 special range covering 550 Kc/s
to 32.0 Mc/s in 6 bands tuned by a 272 pF gang. I.F osc coils can be used for BFO use,
but our HSO units are especially recommended for this purpose.
For the 'Ham' enthusiast, BANDSPREAD HAMBANDS coils are available, tuned by a
special 6/20 pF gang. I.F frequencies are again 460 Kc/s and 1.620 Mc/s, the 1.620 Mc/s
frequency being preferred for low level second channel interference
'STABQOIL' and 'QOILMAX' RANGES AVAILABLE:
Broadcast Bands:
Broadcast Bands:
AERIAL:
LZ - low impedance primary winding 75 ohms, MZ - medium impedance primary winding 600 ohms, HZ - high impedance primary winding
Mixer:
MX - medium impedance primary winding
Oscillator:
OS/46 = tracks at 460 Kc/s, OS/16 = tracks at 1.6 Mc/s
Bandpass:
Use secondaries of aerial coils
Bandspread:
As above but no HZ windings
N.B - HZ available only in types 8, 9, 10, 22, 23, 24.
Colour Code for Standard 'Qoilmax' and 'Stabqoils'
TYPE
LZ
MZ
HZ
MIXER MX
OSCILLATOR
PRIMARY
Aerial
White
Yellow
Pink
Anode Blue
Anode Blue
Earth
Brown
Brown
Brown
HT+ Red
C.Padder Black or Earth
SECONDARY
Grid
Green
Green
Green
Green
Grid C Green
Earth
Black
Black
Black
Black
Padder Yellow
Note: PRI - coupling winding, SEC - tuned winding. HT can be applied to either circuits where circuits require
All oscillator coils have been carefully designed to give as constant an oscillator voltage as possible and our recommended valve circuits and padder values
should be used for optimum results. For 1.4v battery valves, HT can be fed through the coupling winding if desired. To assist oscillation at the higher
frequencies we use a special 4K induction load resistor. OSC grid current for the general coverage coils will average 0.2mA to 0.4mA through a 47KΩ grid
leak, with 200v HT line and 33KΩ OSC anode load. For Bandspread Hambands the OSC HT line MUST BE STABILISED at 150v with an OSC load of 4KΩ
which should be our miniature wire wound inductive type and grid leak of 33KΩ. Grid current will then average 0.3mA to 0.4mA. If other OSC injection volts are
required the OSC anode load can be altered to suit. All coils for the Band Spread Hamband ranges have been specially designed to enable 170° of
BANDSPREAD to be obtained in conjunction with the special 6/20 pF gang and perfect tracking of the RF and Mixer stages with the OSC stage has been
obtained by the careful choice of series & parallel Cs. The two lowest frequency ranges have fixed padders but for 40, 20, 15 and 10m adjustable 10/45 pF
padders are recommended for ease of setting band edges.
GENERAL COVERAGE TYPES - STABQOILS AND QOILMAX
FOR BROADCAST RANGES (VALVE CIRCUITS)
(Prefix code by type letters e.g. LZ,OS)
AERIAL and MIXER SECTION. Figs. 1, 2, 3 or 4
460 Kc/s IF OSCILLATOR SECTION
Max
Ct.
Max
Max
Ct
C
Type
Frequency
'L'
CC
Unl
Series
Type
'L'
CC
pd
No.
Coverage
µH
pF
'Q'
C pF
No.
µH
pF
pF
Notes
Fig.
8
150 Kc/s - 400 Kc/s
3200
25
120
Nil
8
500
40
110
FOR
6
9
530 Kc/s - 1.57 Mc/s
260
15
205
Nil
9
155
15
270
USE
6
10
1.5 Mc/s - 4.4 Mc/s
32.5
15
170
Nil
10
24
20
1000
WITH
5
11
4.1 Mc/s - 12.0 Mc/s
4.3
15
150
Nil
11
3.95
30
3000
10 to
5
12
11.5 Mc/s - 32.0 Mc/s
0.55
20
175
Nil
12
0.54
20
3900
320pF
5
13
6.0 Mc/s - 18.0 Mc/s
2
15
165
Nil
13
1.86
15
3900
GANG
5
AERIAL and MIXER SECTION. Figs. 1, 2, 3 or 4
1.62 Mc/s IF OSCILLATOR SECTION
Max
Ct.
Max
Max
Ct
C
Type
Frequency
'L'
CC
Unl
Series
Type
'L'
CC
pd
No.
Coverage
µH
pF
'Q'
C pF
No.
µH
pF
pF
Notes
Fig.
8
150 Kc/s - 400 Kc/s
3200
25
120
Nil
15
107
40
51
USE
6
9
530 Kc/s - 1.57 Mc/s
260
15
205
Nil
16
64
20
87
10 to
6
10
1.5 Mc/s - 4.4 Mc/s
32.5
15
170
Nil
17
13
25
270
320 pF
6
11
4.1 Mc/s - 12.0 Mc/s
4.3
15
150
Nil
18
3.3
15
650
GANG
5
12
11.5 Mc/s - 32.0 Mc/s
0.55
20
175
Nil
19
0.54
20
1100
5
BANDSPREAD HAM BANDS TYPE - STABQOILS AND QOILMAX
AERIAL and MIXER SECTION. Figs. 11 (Any IF)
Frequency
Max
Ct
Bandspread
Type
Coverage
'L'
Unl
CC
Series C
Hamband
No.
Mc/s
µH
'Q'
pF
pF
160m
1.8
1.8 - 2.0
160
180
15
Direct
80m
3.5
3.5 - 4.0
40
170
14
Direct
40m
7
7.0 - 7.3
12
165
16
20 for C1
20m
14
14.0 - 14.4
3
160
16
20 for C1
15m
21
21.0 - 21.5
1.4
170
16
20 for C1
10m
28
28.0 - 30.0
0.7
175
15
51 for C2
1.62 Mc/s IF OSCILLATOR SECTION. Figs. 9
Osc. Frequency
Max
C
Coverage
L
Ct
Ct
pad
OS Type
Hamband
(Mc/s)
µH
pF
pF
pF
No
160m
3.42 - 3.62
30
4/20
50
650
1.8/16
80m
5.12 - 5.62
19
4/20
20
430
3.5/16
40m
8.62 - 8.92
5
4/20
75
270
7/16
20m
15.62 - 16.02
1.3
4/20
110
200
14/16
15m
22.62 - 23.12
0.85
4/20
100
100
21/16
10m
29.92 - 31.62
0.65
4/20
20
110
28/16
460 Kc/s IF OSCILLATOR SECTION. Figs. 9
Osc. Frequency
Max
C
Coverage
L
Ct
Ct
pad
OS Type
Hamband
(Mc/s)
µH
pF
pF
pF
No
160m
2.26 - 2.46
96
4/20
20
430
1.8/46
80m
3.96 - 4.46
30
4/20
-
2000
3.5/46
40m
7.46 - 7.76
19
4/20
75
270
7/46
20m
14.46 - 14.86
1.3
4/20
134
350
14/46
15m
21.46 - 21.96
0.85
4/20
100
100
21/46
10m
28.46 - 30.46
0.65
4/20
20
134
28/46
NOTE: It is very important to appreciate how small is the tuning C swing (a matter of only a few pFs in 40) therefore particular attention to short
wiring leads and firm fixing of components is vital. Use highest quality materials throughout and modern miniature valves, especially
NUVISTORS and the FRAME GRID types. A STABILISED 150v HT SUPPLY MUST be used for the oscillator with C & R values as Fig. 9.
Thorough screening is essential to obtain maximum gain without RF instability.
To view the recommended circuits click the relevant Figure numbers: Figs 1 to 4 Figs 5 to 9 Figs 11,12 & 15
Thanks go to Ron Bryan for his help on providing the data for this page
