The Four Metres Website

Microwave Modules MML 144/100 mods for 4 m

Paul PA0OCD — Mon, 06 Feb 2012 01:11:00 +0000

Modification at your own risk (yes!) of the Microwave Modules MML144/100 Linear to 70 MHz.

First I tested this (second hand) PA on 144 MHz and on 13.8 V it produced max about 60 W! Perhaps the SRF 1397 is not (and never was) up to 100 Watts hi. This PA 144/100/1/2 is old and has no Preamp, so it can be that later produced PA's have a different PCB Layout....

I modified this 144 MHz PA to 70 MHz using from the “4 Meter Website” both the diagrams and remarks / description (Tnx!) given by SV1DH and GI0GDP. This modification has now become a kind of mixture....

The result is a a 70 MHz PA which has about 10 dB gain and is up to 50 W reasonable Linear and can produce about max 70 W and 10 A at 13.8 V (saturation). The idle current for the PA transistor on TX is about 250- 300 mA (see potentiometer A). Using PSK31 to measure the third order IMD I found IMD-3 at -30 dB (good) at about 15 W output on a normal (slow) Watt-meter and about -20 dB at 20 W output.

The SWR at the input is about 1 to 1 when carefully adjusting the 60 pF Trimmers at No. 2 and No. 3.

Use at the output the 3 coil/2 Doorknob Capacitor Low-pass Filter described by OZ2M or the 3 Coil/ 2 PCB Capacitor Low-pass filter of IK0VAQ. The Doorknob Filter I made here is up to 100 W easily. I saw other filter on the 4 Meter website from G4CJZ and GI0GDP as well.

I made two photos of the modified PA with and without numbers at the places of the modifications:There is plenty of room in this PA!

By the way: Before you start take good pictures of the original PA, I did not hi. And while most of the radio-amateurs are human, like me, we can make mistakes so following this description of the modification hereunder is fully at your own risk.

A lot of the original parts can stay in place (hurrah!) , but I removed:

At 2: remove the 470 pF ceramic capacitor.
At7 : choice: or remove the original 60 pF trimmer or replace it with a low-loss Teflon trimmer of 60 pF.
At 14/14A: remove the silver-mica from PCB track to Ground.
At 17B: remove the 470 pF ceramic capacitor and put a piece of wire in place or leave the 470 pF here.

Now a few changes:
>No. 1A: cut the PCB track located under Coil 1.

>No. 1 = simple Low-pass input filter 50-50 Ohm (Tnx Elsie) with about 20 dB attenuation of 140 MHz.

4 Turns 1.3 mm CuAg 8 mm diameter, long about 17 mm and at both sides 100 pF Silver-mica form the coil to ground. Perhaps SMD capacitors size 1206 and 50 V can also be used here.

>No. 2: 60 pF low Loss trimmer Capacitor, probably Teflon, in series with the track at the place of the original 470 pF capacitor. Remove this one.

>No. 3: 60 pF Low loss trimmer Capacitor from the PCB track to ground.

>No. 4 : 100 nF SMD 1206, 50 volts or better, between ground and the Bias- track to the new 10 uH coil going to the base of the PA transistor.

>No. 5A and 5B: cut the track of the original PCB etched Bias- coil going from the Bias Regulation to the base of the PA transistor.

>No 5: new 10 uH coil, replaces the original PCB coil, made from an old ferrite choke of about 50 uH 1.5 amp, by peeling 2/3 windings of.

>No. 6 A: cut the PCB track under the coil at No. 6.

>No 6: Coil 2 turn 1.3 mm CuAg 8 mm Diameter, long 9 mm

>No. 7: 60 pF Trimmer Capacitor from PCB track to ground

>No. 8: just under and beside (left) of No. 7, a 470 pF SMD 1206 from PCB track to ground or use the removed 470 pF ceramic C.

Leave about 25mm PCB track between Capacitors No.7 / 8 and the base of the PA Transistor .

>No. 9: New collector coil 8 Turns 1.3 mm CuAg 6.5 mm diameter, long 18 mm

>No. 10: 2 x 100 nF SMD 1206 and 2x 4n7 SMD 1206, 50 volts Capacitors from collector-coil No. 9 to ground.

>No 11a: Cut the PCB track between the two sets of the original silver-mica capacitors (at the collector side of the transistor) and place here coil no 11.

>No. 11: Coil 1 Turn 1.3 mm CuAg 1.3mm, about 5 mm long

>Leave between the end of Coil 11 and the capacitors at no 12 about 25 mm PCB track and cut it there at 13 A.

>No. 12: 2 x 180 pF brown Silver-mica 500 volt from PCB track to ground.

>No. 13 A: Cut PCB track under coil No. 13

>No. 13: Coil of 4 turns 1.3 mm CuAg diameter 6.5 mm, long about 10 mm.

>No. 14/14 A: Remove

>No. 14: Small low loss 10 pF Teflon trimmer from coil 13 to ground.

>No. 15 A: cut PCB track under Coil 15.

>No.15 : Coil 4 turns 1.3 mm CuAg Diameter 6.5 mm, long 10 mm

>No. 16 : Small low loss 10 pF Teflon trimmer from coil No. 15 to ground

>No. 17a: cut PCB track under 60 pF air-trimmer.

>No. 17 : 60 pF air-trimmer.

> No. 17 B: Originally there is after this coil No. 17 an 470 pF capacitor place in series with the PCB track. I removed this one and connected both sides of the PCB track with a piece of wire. Perhaps this (original) capacitor can stay.

>No. 18: Not (yet ?) solved, is the VSWR shut-down now, never tested it when the PA was still original though for the 2M Band. Did a short test without a dummy connected at the output, but the shut-down did not work, but the PA is still ok though hi.

>at A: Resistor trimmer for the Idle Bias current. Fully Anti-clockwise first (lowest current without any RF drive) then move the trimmer a bit up clockwise so that there is an increase in current of 250-300 mA (at 13.8 V).

>at B: Resistor trimmer for the Vox-delay. Put it at about 2/3 clockwise, Delay is ok then. When put to much anticlockwise, so with very short delay, I had problems that it would fall off
sometimes....

Success, it looks a lot of work but it is not!

Beacon list

Bo OZ2M — Thu, 02 Feb 2012 00:52:00 +0000

Beacon List

Most Wanted VUSHF DX

Bo OZ2M — Wed, 01 Feb 2012 20:58:00 +0000

Most Wanted VUSHF DX including 70 MHz squares and DXCCs

Italy, San Marino, SMOM and Vatican back on 4 m

OZ2M — Wed, 01 Feb 2012 19:22:00 +0000

Piero, I0KPT, reports that Italy is back on 4 m again from 1056 UTC on 1 February 2012 and until 31 December 2012. Frequencies, power and geographical restrictions are the same as in 2010.

Please be informed that, following our extraordinary authorization request for amateur radio propagation experiments in the 70 MHz band, submitted to the Economic Development Ministry - Telecommunications Department, the General Directorate for Electrical Communications and Broadcasting Services, Division II, has authorized said experiments in period 1 February - 31 December 2012.
The experimental campaign will be possible thanks to the participation of the ham radio community , with stations scattered all over the globe. In particular, activities will be aimed at experimenting the transequatorial and the sporadic-E propagation mechanisms.

Prof. Piero Tognolatti

More information can be found here here.

Tony, I0JX, reports that the I0JX/B beacon is also back on the air. Tony also informs that the permit includes the Sovereign Military Order of Malta and the Vatican. Although not yet announced, one should reasonably expect that also the San Marino hams are authorized to operate on 70 MHz (as they were during all the past Italian experimental periods).

International 70 MHz allocations

Bo OZ2M — Wed, 01 Feb 2012 14:56:00 +0000

International 70 MHz allocations

Czech Republic also on 4 m in 2012

OZ2M — Fri, 30 Dec 2011 21:27:00 +0000

Ondra, OK1CDJ, confirms that individual radio amataurs in the Czech Republic will also have access to the 4 m band in 2012 with the same conditions as in 2011.
Furthermore, will the beacon OK0EE continue its operation in 2012 too.

The Netherlands on 4 m in 2012

Bo OZ2M — Fri, 30 Dec 2011 13:33:00 +0000

All Full Class radio amateurs in The Netherlands will have access to the 4 m band from 1 January 2012. The frequency allocation is 70,0 to 70,5 MHz and with a maximum power of 50 W PEP. Cross band and duplex contacts are not permitted.
Regeling van de Minister van Economische Zaken.

Italy back on 4 m in 2012

Bo OZ2M — Sun, 25 Dec 2011 22:44:00 +0000

Great news from Italy. Professor Piero Tognolatti, I0KPT, has informed that the Italian military authorities have granted the use of the 70 MHz band in Italy for period 1 February - 31 December 2012 (thus covering the transequatorial propagation period). The authorization is about to be issued by our Telecommunications Ministry. Please note that the authorization has not yet been issued at the time of writing!

The University of l'Aquila announces that the military authorities have accepted their request to carry out experiments on the 70 MHz band:

Experimental radiopropagation activities on the 70 MHz band
Students of the concerned courses please be informed that, following an extraordinary authorization request for experimenting radio propagation in the 70 MHz amateur band, forwarded to the Ministry of Economic Development - Department of Communications, the entitled military office expressed its agreement to the requested authorization, which will be valid 1 February through 31 December 2012. We are awaiting the completion of the authorization process on part of the Ministry.

The experiments will be possible thanks to the participation of the worldwide amateur radio community with their stations scattered all over the globe. We will try to exploit, in particular, the tropospheric and
sporadic-E propagation modes.

Professor Piero Tognolatti (I0KPT)

Director of Electrical Engineering and Information Department, and full Professor of Electromagnetic Fields at the Università dell’Aquila.

More information in Italian.

Beacon QRV on 4 m from Bahrain

Bo OZ2M — Fri, 23 Dec 2011 18:20:00 +0000

David, A92IO, reports that a new, and first in Bahrain, beacon will be on air with the call A92C/B and located in LL56HE. David will be back in Bahrain after New Year and plan to install the beacon sometime during January 2012 when time permits. The operating frequency will be 70,085 MHz.
The beacon hardware is a Storno CQF 632 prepared by Henning, OZ1JXY.

Distance Records

Bo Hansen OZ2M — Sat, 17 Dec 2011 13:54:00 +0000

70 MHz Distance Records

Hungarian 4 m beacon on air

Bo OZ2M — Sat, 26 Nov 2011 13:44:00 +0000

Peter OE5MPL reports that Gabi HA1YA on 24 November 2011 got a licence for his 4 m beacon HG1BVC/B on 70,060 MHz locator JN87FI 725 m asl. It will be on air as soon as time permits.

IARU Region 1 bandplan

Bo OZ2M — Sun, 25 Sep 2011 23:11:00 +0000

Frequency	Bandwidth	Mode	Usage
70.000 70.090	1000 Hz	Telegraphy, MGM	Coordinated beacons
70.090 70.100	1000 Hz	Telegraphy, MGM	Personal beacons 70.091 MHz +/- 500 Hz WSPR beacons
70.100 70.250	2700 Hz	Telegraphy, SSB, MGM	70.185 Cross band calling 70.200 CW/SSB calling 70.250 MS calling
70.250 70.300	12 kHz	All modes	70.260 AM/FM calling 70.270 MGM activity centre
70.300	12 kHz	All modes	70.300 RTTY/FAX
70.300 70.500	12 kHz	FM channels 12.5 kHz spacing	70.3125 Digital communications 70.325 Digital communications 70.450 FM calling 70.4875 Digital communications

New IARU Region 1 bandplan for 4 m

Bo OZ2M — Sat, 24 Sep 2011 14:22:00 +0000

A new bandplan for 4 m has been made by the IARU Region 1 VHF Committee.

Spain has applied for a continuation on 4 m

Bo OZ2M — Sun, 24 Jul 2011 20:03:00 +0000

Spain lost its access to the 4 m band on 1 July 2011 but at the same time URE applied for a continuation and wider allocation too.

"Hams still interested in using this band, but after the experience last year we found that the current allocation of this band is somewhat problematic, as being the only frequency 70,200 MHz common to all countries that have authorized their amateurs of all or part of the band from 70,000 to 70,500 MHz, congestion occurring at this frequency (70,200 MHz) during sporadic E openings through the summer months to prevent proper use of it.

On the other hand, the European Radiocommunications Office (ERO) in the study conducted in 1995 called "Detailed Spectrum Investigation (DSI)," recommends allocating a minimum of 100 kHz, preferably centered at 70,2 MHz title secondary.

For these reasons, we request the extension of the band segment 70,150 to 70,250 MHz, i.e. 50 kHz on both sides of the common frequency of 70,2 MHz

Waiting to be embraced our request, greets atte.,

Salvador Bernal Gordillo, EA7SB
Secretary-general"

(via Google translate)

The Netherlands continue its way towards 4 m

Bo OZ2M — Sat, 23 Jul 2011 12:33:00 +0000

In The Netherlands the process towards opening the band to radio amateurs continues and another step has been completed by publishing a new national frequency plan in the STAATSCOURANT 6 July 2011.

It is important, however, to emphasise that no license has yet been issued and there are more steps to complete including the regulator to issue new rules and a three months standstill period.

Towards an extension of the 4 m band in Belgium

Jean-Jacques ON7EQ — Fri, 22 Jul 2011 22:43:00 +0000

I am pleased to inform you that we have a good chance to see the 4 m band in ON-land being extended in a near future!

For the moment, only 69.950 MHz is allowed on a 'trial basis' and subject to prior notification.

In the name of UBA, a request for extension of the band was introduced in May 2011 to the national telecom authority 'BIPT'.

This request is currently being examined, most probably a 'public enquiry' procedure will follow soon. There is a good chance that the full band will be allocated, except perhaps some segment(s) reserved for existing users.

Bahrain on 70 MHz

Bo OZ2M — Sat, 18 Jun 2011 05:34:00 +0000

Dave, A92IO, writes that Bahrain is now on 70 MHz too. The allocation is from 69,9 MHz to 70,4 MHz and with a maximum power of 500 W. The allocation is on a secondary and non interfering basis.
Already two firsts have been worked between Bahrain (A92IO) and the Czech Republic (OK1KT) and Slovakia (OM3PV). Both contacts were made on 2011-06-03 at 0812 and 0828 UTC respectively.

70 MHz Equipment

Allan GM4ZUK — Fri, 27 May 2011 03:48:00 +0000

70MHz Equipment

Antennas

Ross G6GVI — Thu, 26 May 2011 22:09:00 +0000

Antennas

Regular net activity on 70 MHz

Ross G6GVI — Thu, 26 May 2011 21:47:00 +0000

Regular net activity on 70 MHz