| |
G8MNY > TECH 05.02.07 08:19l 59 Lines 2392 Bytes #999 (0) @ WW
BID : 1479_GB7CIP
Read: DL8FBH GUEST DL1GMC OE7FMI
Subj: Drake TC-3300-LP QRO LP Filter
Path: DB0FHN<DB0MRW<OK0PKL<OK0PCC<OM0PBC<OK0PPL<DB0RES<TU5EX<IW8PGT<VK4TRS<
GB7YFS<GB7CIP
Sent: 070205/0029Z @:GB7CIP.#32.GBR.EU #:1479 [Caterham] $:1479_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EU
To : TECH@WW
By G8MNY (Corrections Jan 07)
(8 Bit ASCII Graphics use code page 437 or 850)
I have reverse engineered this QRO HF Tx filter. It was used with a QRO PA & it
is nice to know, that no matter what QRM you may cause other HF users, above HF
all is quieter than can be measured!
The specification is 1KW MAX @ HF, Attenuation > 80dB above 41MHz.
Through loss is practically unmeasurable.
0dB_³___________________
-3dB´ `\
-10dB´ |
-20dB´ |
-40dB´ |
-60dB´ |
-80dB´ V~-._
ÅÄÄÂÄÄÂÄÄÂÄÄÂÄÄÂÄÄÂÄÄÂÄÄÂÄÄÂÄÄÂ Freq
0 5 10 15 20 25 30 35 40 45 50 MHz
THE CIRCUIT
This is a type of M derived Low Pass filter.
L2 L3 L5 L6 Coils are silver plated 3mm í wire.
o)ÄÂÄ(((()ÄÂÄ(((()ÄÂÄ(((()ÄÂÄ(((((ÄÂÄ(o L1 = L7 = 0.3uH, 8.5 T on 9mm former.
³ ( === ( C4=== ( ³ L2 = L6 = 0.4uH, 7 T on 15mm former.
³ ( L1 ³C2 ( L4 ³ L7 ( ³ L4 = 0.13uH, 3.5 T on 9mm former.
³=== C1 ³ === C3 ³ C5 ===³ L3/5 = 0.4uH each, wound as centre
ÀÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÁÄÙ tapped of 15T on 15mm former.
C1 = C5 = 53pF bolted though Mica washer disk.
C2 = C4 = 186pF bolted through double sided Mica washer disks.
C3 = 124pF larger bolted though Mica washer disk.
The 3 shunt traps L1/C1, L4/C3, & L7/C5 all resonate at 40MHz.
PHYSICAL CONSTRUCTION
SO239³ L2 ³ L3 L5 ³ L6 ³SO239
ÚÄÄ´ /~|||||| º³º /~||||||| ||||||| º³º ||||||~\ ÃÄÄ¿
³ ³] |||||| [º³º] ||||||| ||||||| [º³º] |||||| [³ ³
ÀÄÄ´ \ |||||_/ º³º ||||||||||||||_/ º³º \_||||| / ÃÄÄÙ
³ ððð ³C2 __/ C4³ ððð ³
³ ððð L1 ³ L4 ððð ³ L7 ððð ³
³ ___\n____C1 ³ ____\n____C3 ³ C5____n/___ ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The SO239s are riveted on, as are the 2 divider plates. The chassis has folded
edges not shown here for simplicity. The U channel shaped cover is screwed on
into the folded edges & it has RF fingering to help ground the 2 central
dividers. The cover is the base mounting. (eg. above is then upside down.)
Why Don't U send an interesting bul?
73 de John, G8MNY @ GB7CIP
Read previous mail | Read next mail
| |
