rf - Free and Open Source Software

Fi ,,"Al SHIELO
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RF Sealing Tape
RF sealing is o ne o f the strategies emplo
yed in build ing tra ns mitters that do not
ge nerate T VI. The u nwanted rf is generated
but the enclosure is designed so it never gets
out.
The same approach is used to bu ild
receivers that do no t respo nd to any rf
excep t that which enters the receiver
thro ugh a coax connecto r, and in the const
ruction o f laboratory signal genera to rs.
But d id you ever try to convert a no n­
shielded enclosu re in to a shield ed enclosu re?
It can be done, bu t ;ften it is a task to make
st rong men weep. Hinges, join ts, ventilation,
d oors, meters, . .. and how abou t shielding
some of the wiring that carries power
through areas ho t at rf?
Scotch Rescue
The 3 M Co m pany has develo ped a remarkable
copper foil tape with an electrically
conductive pressure sens itive adhesive.
The tape adheres directly to clean
metal with a good low resistance electrical
connectio n between metal and co p per foil.
The tape can im prove leaky shielding by up
to 60 dB . It is designated "Sco tch" Brand
Electrical Tape No. X-lI BI and comes in 54
foot ro lls o f assorted wid ths.
The tape is used alone. o r with perforated
or solid aluminum sheet. The sheet is available
in most hardware stores. It is cut into
sections, shaped to fit, and taped in place.
Large shield ing assem blies can be made u p
from smaller o nes. You must wash the
aluminum wit h detergent to ge t any o ils off
befo re taping.
rr One approach to red ucing pickup by
power or co n tro l wiring in transmitters is to
use shielded wire. This is horrid stuff to
work with, if you have ever tried it. A piece
o f o rdinary hookup wire can be laid alo ng
the chassis and covered with a strip o f shield
tape, to achieve the sa me result.
CH ASSIS
CH ASSI S
FOIL TAPE
Donald Kerr, WA3BDI
State College. Pennsylvania
DUAL GATE MOSFET
PRE-AMPS
(
•
•
to 175 MHz, $19.95 ppd.
to 300 MHz. $23.95 ppd.
to 400 MHz. $27.95 ppd.
to 450 MHz. $31.95 ppd.
• Available from 5 MHz. to 450 1104Hz. Bandwidth is
a p prox imately 3')'. of frequency.
• Voltage g a in 30 to 40 DB d e pending on frequency.
• Two Dual Gat. MOSFET a m plifier dag es with e a ch
having a tuned input and tu ned output . Each Dua l
Gate MOSFET Is actually an Inte gra ted cascode circ
uit thus glvln9 you 2 cascade ci rcuits equivalent
to 4 t riodes.
• Exc epti ona lly low noise (2.5 DB at 175MHz.), greatly
reduced crou mod ulation a nd 10 t imes t he d y­
namic range (si 9 na l handling ca pab ility) of the b est
b i-polar transistors. Also superior to preamps using
'Iunctio n FETs and SingI. Gate MOSFETs.
• nterna l connections fo r high Impeda nce AG e or
ma nua l q a ln control if need.d .
• Type BNC input a nd outp ut recepta cles for minim um
lou at UHF. Standard Impedance Is 50·75 ohms.
• Carefully tuned at o ur laboratory with sweep generator
a nd osci llo scope fo r t he best bandp4u
Istre .
• Full W4 ve UHF diodes protect input transh tor.
• Oper4tes o n 6 to 16 vo lts DC,S to IS Ma.
character­
VANGUARD LABS
Dept. H
196·23 Jamaica Ave., Hallis, NY 11423
"TOWER HEADOUARTERS'"
11 Brands! HEIGHTS al u minum 35% off!
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S tanley. W isconsin 5476 8
· GO VHF
Go YlIF the easy YH F A 5> (l cl . t e ~ wa ~·. Send tor delc rlDth e
Technical Hutletlns de.crlbln5: our eom otete line or TRA:-:­
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}'REQt:ES CY )It:LTIPLIERS ror 50, IH. 220. n2 and
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P.O. 801 22135. DENVER, COLORADO 80222
-
MAY 1969 121