QRP PROJECT ZM-4, Manual

5

the marked with 1, the tap to number 5 and the longer end to number 20.

[  ] Transformer FT43-37

Only a few parts to be mounted now. Varables, Switches and Jacks. All switches 

must be connected to the corresponding solder points at the PCB by pieces of the 

shipped CuAg wire. The upper row of the switch connectors belonge to the inner 

part of the PCBm the lower switch connectors to the holes placed more to the edge 

of the PCB. Befor you can mount the remainig parts now you must prepare the 

enclosure. The picture in the appendix is not 100% on scale, you must do your own 

measurements!!

Start with the BNC jacks at the back side:

[  ]  BNC out 

[  ]  BNC IN

[  ]  SW2 (only 1 row of PINs.)

[  ]  SW5  ( switch wit 2 rows of PINs but mechanically NO Mid Point for switching.

Do NOT interchange the switches with the other 2 row switch which can be 

switched up/down/middle!!! 

[  ]  Mount the two banana jacks (red and black) corresponding to the „rot“ (red) and 

„schwarz“ (black) points on the PCB. Take care to mount them using the isolation 

parts!. 

[  ] solder a piece of red and black wire 2-3cm each into the holes marked rot (red) 

and schwarz (black)

Now the front side:

[  ] SW4 two row switch with middel switch point

[  ] SW1two row switch with middel switch point

[  ] SW3 two row switch NO!!  middel switch point

Now the variable )Polyvaricons) The use 1 solder tap at the front side and two a the 

back side. The single solder tap in front must pe placed directly to the PCB, the 2 

taps are 2cm above the PCB. Solder the single front tap direcktly to the PCB and 

each of the two upper solder taps by using a 2cm piece of bare wire between the 

Taps and the corresponding holes C2B/C2A und C1B/C1A. Take the full length of 

the taps to solder. Take care not to make a short between the wires and the small 

nuts at the backside of the Polyvaricon.

[  ] Drehko 2, 3 taps

[  ] Drehko 1, 3 Taps

In the hole just below the resistors between SW1 and C1 (labeled LED) you must 

solder a 5cm long piece of wire.

Before you put the PCB into the enclosure check the solder side of the PCB if all 

wires have been cut very short directly above the solder! If they are too long they 

may produce a short betwwen PCB and enclosure. If ok, set the PCB in the slot, 

there is only one slot fitting exactly.

At the backside connect the red wire with the red banana jack and the black wire 

with the red banana jack. (Did you mount the banana jacks isolated from the 

backplane?? You should do, otherwise your feeder would be shorted :-)

Now there is only one part remaining, the LED. Connect the short leg of the LED 

(cathode) to the wire you have soldered to point marked LED on the PCB and the 

long leg (Anode) end to the connection point at the edge of the PCB immediately 

between SW1 and C1. You may need a small additional piece of wire to effect the 

latter connection

Now you can use your ZM4

Connectors and switches

Front left to right:

SW4

SW4 has 3 position: Up middle down. SW 4 is used to enable 80 and 40m. 

Which position is  to be used depends on your antenna length, it must be found 

experimental. Middle will work with most antennas for 10-40m If the wire is long 

enough, it will also be ok for 80m. In any cas e of 160m and very often for 80m you 

will have to use up or down, both of them add extra capacity.

C2

C2 ist the maincapacitor. It is used to resonate ZM4. C2 and C1 interact so you 

must tune then both. After some training, you will be find it to be very fast tuning. 

Best way is to pretune in receive mode. Try to find nois or signal maximum. If you 

have found it switch to tune and do fien tuning while you transmit with little power.

C1

C1 ist is the coupling capacitor. See description of C2

S1

S1 Adds extra capacity to C1 Normaly Middle is ok, only if your antenna is very 

short or it´s impedynce is very low the upper and lower switch position will help.

S3

This switch is good to switch between Operate and Tune. In TUNE a 50 Ohm 

resistive bridge is switched in. This prevents you PA because even with a shortened 

Antenna ot a missing antenna your PA never will see a VSWR worse then 2 (25 

Ohm if shortened and 100 Ohm if open) At the same time it acts as a the measuring