Bert Modderman Engineer


Products for Sale
10GHz amps
13cm 40 watt
MRF284 proj.
Coax adapters
Lot sales
Custom build
Customer Pics

Preamps etc
23cm preamp
23cm dvb downc.

2m/70cm filters
6cm filters
9cm filters
13cm filters
23cm filters
1090MHz fil.

Slot Antenna's
10ghz septum
linear feeds
8420mhz sep.
6cm septum
Dish calcs.
Quad ant.

Roller Button

ATV Hobby
Dro Modulator
Echostar Mod
Received ATV



added a new section linear feeds and coax adapters.
a new product, waveguide to round transitions, added to waveguide page in antenna section. link => Waveguides
mrf21030 page added. for those that have mrf21030 fets laying around.
8 watt amps for 10ghz can now be ordered. 100mw in 8 watt out, price 475 euro.
10ghz 16 watt is also possible.
9cm septum has been made, picture of it on the flickr site.

Added to lot sales section:
Amphenol Connex Male N connectors 4.50 euro / piece..
with extended teflon 5mm and 4mm extending centerpin.
digikey sells them for 8 euro. no chinese ebay crap. solid fit.

updated 23cm filter section.
i sell very low loss filters for 1296mhz ssb 100 euro!

Dont forget to take a look at flickr, the place where i store my latest photo worthy objects i have made

Received my third batch of these little RA18H1213g pcb's last week.
they where sold out again.
the pcb's can be used for the ra18h1213g ra60h4452m1 ra60h4452 RA30H4047 RA30H1317M RA30H1317
and with a small rearrangement of components, also for m57762.

The new copper base in the 250 watt amplifiers work realy nice.
I have been contacted if i could make heat spreaders as well for a MRFE6VP61K25HR5.
They can now also be ordered for 80 euro. tapped and drilled 80mm x 120mm x 10mm thick.
I also make watercooled versions for 160 euro. that part would become 2cm thick.
See the MRFE6VP61K25HR5 link for pictures of the waterblock.
I can also make heatspreaders for other projects you need, just send me a drawing.(8 cm wide preferred)
Amp below is the 250 watt 23cm amp.

Circulators, 300 watt ssb 0.25db loss for 1296-1298 mhz.
the 1296 are 50 euro a piece, endless stock and i can also get circulators from 144mhz to 2.3ghz. in various sizes.
also available with box with N or sma connectors and or 250 watt terminator as shown below for 135 euro.
losses are about 0.3 to 0.35 db for a circulator in an alu box.

1296 mhz combiners with forward and reflected in the 500 watt hybrid.
these can be used to combine 2 250 watt amplifiers for a combined output power of 500 watt.
usualy there are losses when coupled but by running the amplifiers on 28.5 volt you can compensate for losses and get 500 watt p1db output.
price of this kit is 150 euro, just pcb is 30 euro and pcb+ resistors 75 euro.

Please dont use transfer relays for my amplifiers. Allthough all ssb amplifiers have bias input that also turns off gain, i dont thrust this to work well.
The relays themselfs are perfect perhaps but because transfer relays connect input to the output of the amplifier, selfdestruction of the amplifier can happen.
The 1kw narda's i had last year are now sold out.

Finaly, i made an amp with extra copper cooling, and didnt expect the results to be so much better.
the amp on the left can do 60 seconds rx and 90 seconds tx continues in 18degree ambient,
the amp on the right with a little bit extra copper can do 60seconds rx and 180seconds tx.
when ambient temp is 15 degrees, 15 minutes of transmitting is possible without tempwarning engaging.
extra copper in the amplifier will be 20 euro extra.

In the milling link on the left i claim to be able to make boxes to your wishes.
Below is another nice example of what i made for a customer.

The 250 watt 3.5 watt in amplifiers for 1296mhz are now 28 volt.
Most amplifiers do even better reaching 280w p1db.
This has been confirmed by several buyers.
The improved amplifier with the new batch of more expensive fets is 520 euro.
Amplifier comes with bias on/off and Temperature warning output.
Suitable heatsinks for this ampifier are menioned in the amplifier section

A bigheatsink can be bought for 90 euro.
It is milled flat and comes with one 12 volt blower and skirts to force air thru the heatsink.
A second matching fan can be added for 16 euro extra.

Designed a new filter for 13cm because the current design i had was very narrow and had to much loss in the passband.
The new design is 2300 to 2400 where 2320 to 2400mhz can be set to 0.75 db loss.
(see curves in the 13cm filter section)

added webchat section!!

A few requests for atv bandpass filters made me take a closer look at the 1296 mhz filter and see if it could be tuned to atv.
Below is the result, a 1245 to 1320mhz bandpass with approx 0.75db loss +/- 0.10db in ripple.
This atv filter is also 100 euro.

Latest version of the 6cm atv transmitter with baseband input.
it has memory, fine steps of 250 khz on 6cm, up down and rotory encoder.
It contains a vco oscillating directly on 6cm.
Other versions can be ordered like on 800MHz, 1GHz, 23cm, 2GHz, 13cm, 3400MHz, 5GHz
The range of the transmitter pcb below is 5100 to 6100mhz. output +/- 5mw
you can also put a seperate doubler behind this to make atv on 10.200GHz to 10.500GHz
(or to 12.200 GHz or even 4x to 24.400GHz but the last is not programmed but can be on demand)
With an extra switch and RF relay you can choose on which band to transmit.
price of this pcb only is 125 euro.
Extra's can be added like switches and buttons or doubler to 10ghz but costs extra.
Also a led display output is possible but will only show 6 digits.

2 cases, one for a M57762 and another for a M67715.
The last one has adjustable bias with a LM317.
Each case is 75 euro with components, connectors but not with module and potmeter..

Ok, copper version now tested and works better, but together with the black heatsink below
it is not possible to do continues 250 watt. but works for jt cw and ssb.
max for JT lies around 1 minuut on and 1 minuut off, during off period the amp must be disconnected from 30 volt.
The heat just remains in the heatsink even with a strong blower.
I must say that i use a high standard and i want to keep the fets cool so they will have a long life.

1296mhz bandpass with 0.45db loss
blocks 430mhz, 900 mhz, 1800mhz and 2300mhz more then 90db. (theoretical)
bandpass is very wide.

After many hours of searching i found heatsinks.
For 75 euro extra i can add this heatsink under most amplifiers.
You can also order them for 75 euro. blower not included

I have ordered a large piece of copper 5cm x 8mm thick for the 250 watt amplifiers.
2 different amplifiers can be ordered.
1 with extra copper for better thermal connection with heatsinks ,400 euro, or the plain ssb version 350 euro.
There will be no aluminium between the fet and the underside of the amplifier.

p1db point of a 250 watt 1296mhz amp at 3.3 watt input and 250 watt output.
this is an old graph though, some amps are superlinear to 250 watt now with p1db above 300.
2 parallel can do 500 watt easy or with 4 amps 1000watt

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