Date   
Re: QO-100 dual band patch antenna

GM6VXB
 


I used an RS two part (not including bolt, nut, and thrust bearing) hole cutter
to make the holes. Got a range of them up to two inch.
Far easier and much safer once the smaller 3/8th hole is
drilled.
And you get a much cleaner hole with no burrs.
 
Martin, GM6VXB

----- Original Message -----
Sent: Saturday, December 14, 2019 3:24 PM
Subject: Re: [UKMicrowaves] QO-100 dual band patch antenna

Use a 22mm Cone (step) drill . It works well with a hand held power drill if you are careful.

73

Barry, G8AGN
On 14/12/2019 15:10, John Worsnop wrote:
That's exactly how I built mine

On Sat, 14 Dec 2019, 14:09 Mike Willis, <willis.mj@...> wrote:
How much power are you proposing to use? Perhaps use PCB for the reflector and brass for the patch. Cutting a square and then cutting the corners off is not that hard. Drilling a 22mm hole is much more difficult.

There is always the alternative of buying one. Not so much fun though.
--
Mike G0MJW

Re: QO-100 dual band patch antenna

Mike Willis
 

It does - I used the same method building an earlier version, but the step drill is also very likely to catch with this sheet metal so extremely important that the metal is clamped well. The human had is a very poor clamp for metalwork and easily damaged. Copper is hard to work with, brass easier. The best material is probably silver but it's a bit pricey.  Scrap silver plate maybe. Try and get something not springy as it won't be easy to bend for adjustment which is likely to be needed is you are not working to CNC precision. 

--
Mike G0MJW

Re: QO-100 dual band patch antenna

Barry Chambers
 

Use a 22mm Cone (step) drill . It works well with a hand held power drill if you are careful.

73

Barry, G8AGN
On 14/12/2019 15:10, John Worsnop wrote:

That's exactly how I built mine

On Sat, 14 Dec 2019, 14:09 Mike Willis, <willis.mj@...> wrote:
How much power are you proposing to use? Perhaps use PCB for the reflector and brass for the patch. Cutting a square and then cutting the corners off is not that hard. Drilling a 22mm hole is much more difficult.

There is always the alternative of buying one. Not so much fun though.
--
Mike G0MJW

Re: QO-100 dual band patch antenna

John Worsnop
 

That's exactly how I built mine


On Sat, 14 Dec 2019, 14:09 Mike Willis, <willis.mj@...> wrote:
How much power are you proposing to use? Perhaps use PCB for the reflector and brass for the patch. Cutting a square and then cutting the corners off is not that hard. Drilling a 22mm hole is much more difficult.

There is always the alternative of buying one. Not so much fun though.
--
Mike G0MJW

Re: QO-100 dual band patch antenna

GM6VXB
 


Mike,
 
Not done a link budget for what I propose for my dish size, but
would not expect to be anything more than five or six Watts'ish.
 
Part of the (initial) excercise is to show my grand daughter that
you do not have to spend money on some parts of the station to
have a reasonable setup as most bits are in my junk boxes (have been
for years).
 
Martin, GM6VXB
 
 

----- Original Message -----
Sent: Saturday, December 14, 2019 1:09 PM
Subject: Re: [UKMicrowaves] QO-100 dual band patch antenna

How much power are you proposing to use? Perhaps use PCB for the reflector and brass for the patch. Cutting a square and then cutting the corners off is not that hard. Drilling a 22mm hole is much more difficult.

There is always the alternative of buying one. Not so much fun though.
--
Mike G0MJW

Re: QO-100 dual band patch antenna

Mike Willis
 

How much power are you proposing to use? Perhaps use PCB for the reflector and brass for the patch. Cutting a square and then cutting the corners off is not that hard. Drilling a 22mm hole is much more difficult.

There is always the alternative of buying one. Not so much fun though.
--
Mike G0MJW

QO-100 dual band patch antenna

GM6VXB
 

Looking at building a QO-100 dual band patch antenna as shown on the uhf-satcom.com
blog on the interweb.
 
The design uses copper (or brass) sheet of which I only have some brass sheet but only
basic hand tools to build so difficult and probably many cuts to the hands before I get one
built..
 
But I do have many sheets of double sided PCB so can afford to do it wrong many times.
 
My query is whether copper clad PCB will work as well as copper/brass sheet.
Brain says it will, but maybe someone knows better than this bodger ?.
 
Martin, GM6VXB

Re: Ionica Power amps

militaryoperator
 


Many thanks Mark, that does clear things up. Will start with the rx unit, then if ok, on to the pa etc. 

cheers, Ben G4BXD


-----Original Message-----
From: Mark GM4ISM via Groups.Io <gm4ism@...>
To: UKMicrowaves <UKMicrowaves@groups.io>
Sent: Fri, 13 Dec 2019 15:22
Subject: Re: [UKMicrowaves] Ionica Power amps

Hi Ben
 
That should be safe but in addition to sequencing of the supplies, the protection that  shuts down the 10V line should the -ve bias fail is highly recommended.
As others have suggested, using the presence of the bias to hold ‘on’ the 10V regulator is a most effective  method and is also suggested on my webpages (John XDYs cct!)   This is also probably the fastest protection, which is important.  The low DC resistance of the devices with no bias means that  for as long as the 10V is still present, very large currents will be  taken.    The RF devices cannot stand this for very long at all.  If the failure mode for the bias is a ramped decrease in voltage (or if there is a moderate capacitance to hold it up for a few tens on mS)   then tripping the 10V  when a bias voltage less than say –10V, should mean that the  10V will be effectively removed before the neg bias drops to a critical level.   The actual device bias voltage is usually less than -3V  and that is regulated down from the -12V
 
As to applying the 5V Tx enable immediately, that  forces the bias to the operating voltage and the devices start to draw significant quiescent current even with no drive. These devices are running close to Class A which means significant dissipation even when  un-driven
My approach is to apply the 10V (after proving the -12V)  and leave it on.  The TxRx switching then unmutes the PA only on transmit.  I use this on numerous PA and it has been most reliable, indeed I have had a bias supply failure on one amp (2.3GHz) with no damage occurring.
Switching both the 10V and Tx enable signal on with the PTT would be OK too I guess.
The effect of unwittingly applying  normal RF drive to the amp with no 10V  present is not known but I would guess it would not cause damage.
 
Good luck with the project and be aware that should the worst happen, there are a small number of spare PA blocks  lurking in Scotland.
Mark GM4ISM
 
 
Sent: Friday, December 13, 2019 12:41 PM
Subject: Re: [UKMicrowaves] Ionica Power amps
 
Getting confused with all these suggestions. The pin outs are stated as:
 
1 RF Detector OP. Approx 6.5V at full op  
2 Info says Ground.. not! leave O/C Bias???  
3 Reset Error output (also used to enable original PSU)  
4 Mute (+5V to transmit)  
5 -12V  
6 0V  
7 +10V  
8 +10V  
9 RF Detector ground  
10 Temperature OP  
11 Error OP  
12 +12V (approx 25mA)  
13 0V  
14 0V  
15 +10V

So, could I connect the  -12v to 5, the +12v to 12,   (the +12 is only logic I think, the pa supply is the +10v)
 
and then switch the +10v to 7/8/15 at the same time as logic 1 on pin 4?
 
Would that result in magic smoke being released?
 
 
Ben
 
 

Re: Ionica Power amps

Mark GM4ISM
 

Hi Ben
 
That should be safe but in addition to sequencing of the supplies, the protection that  shuts down the 10V line should the -ve bias fail is highly recommended.
As others have suggested, using the presence of the bias to hold ‘on’ the 10V regulator is a most effective  method and is also suggested on my webpages (John XDYs cct!)   This is also probably the fastest protection, which is important.  The low DC resistance of the devices with no bias means that  for as long as the 10V is still present, very large currents will be  taken.    The RF devices cannot stand this for very long at all.  If the failure mode for the bias is a ramped decrease in voltage (or if there is a moderate capacitance to hold it up for a few tens on mS)   then tripping the 10V  when a bias voltage less than say –10V, should mean that the  10V will be effectively removed before the neg bias drops to a critical level.   The actual device bias voltage is usually less than -3V  and that is regulated down from the -12V
 
As to applying the 5V Tx enable immediately, that  forces the bias to the operating voltage and the devices start to draw significant quiescent current even with no drive. These devices are running close to Class A which means significant dissipation even when  un-driven
My approach is to apply the 10V (after proving the -12V)  and leave it on.  The TxRx switching then unmutes the PA only on transmit.  I use this on numerous PA and it has been most reliable, indeed I have had a bias supply failure on one amp (2.3GHz) with no damage occurring.
Switching both the 10V and Tx enable signal on with the PTT would be OK too I guess.
The effect of unwittingly applying  normal RF drive to the amp with no 10V  present is not known but I would guess it would not cause damage.
 
Good luck with the project and be aware that should the worst happen, there are a small number of spare PA blocks  lurking in Scotland.
Mark GM4ISM
 
 

Sent: Friday, December 13, 2019 12:41 PM
Subject: Re: [UKMicrowaves] Ionica Power amps
 
Getting confused with all these suggestions. The pin outs are stated as:
 
1 RF Detector OP. Approx 6.5V at full op  
2 Info says Ground.. not! leave O/C Bias???  
3 Reset Error output (also used to enable original PSU)  
4 Mute (+5V to transmit)  
5 -12V  
6 0V  
7 +10V  
8 +10V  
9 RF Detector ground  
10 Temperature OP  
11 Error OP  
12 +12V (approx 25mA)  
13 0V  
14 0V  
15 +10V

So, could I connect the  -12v to 5, the +12v to 12,   (the +12 is only logic I think, the pa supply is the +10v)
 
and then switch the +10v to 7/8/15 at the same time as logic 1 on pin 4?
 
Would that result in magic smoke being released?
 
 
Ben
 
 

Re: GB3PKT

Ralph
 

Propagation over the past few days has been awful, I do not

Think that will help reception very much, just a thought hi

Seasons greetings

73

Ralph G4ALY

 

Sent from Mail for Windows 10

 

From: John Lemay
Sent: 13 December 2019 12:47
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] GB3PKT

 

Seems to me that GB3PKT on 3cms is weaker than usual. But in case it's an RX

problem here, does anyone else concur or disagree ?

 

Regards

 

John G4ZTR

 

 

 

 

 

GB3PKT

John Lemay
 

Seems to me that GB3PKT on 3cms is weaker than usual. But in case it's an RX
problem here, does anyone else concur or disagree ?

Regards

John G4ZTR

Re: Ionica Power amps

militaryoperator
 

Getting confused with all these suggestions. The pin outs are stated as:

1 RF Detector OP. Approx 6.5V at full op  
2 Info says Ground.. not! leave O/C Bias???  
3 Reset Error output (also used to enable original PSU)  
4 Mute (+5V to transmit)  
5 -12V  
6 0V  
7 +10V  
8 +10V  
9 RF Detector ground  
10 Temperature OP  
11 Error OP  
12 +12V (approx 25mA)  
13 0V  
14 0V  
15 +10V

So, could I connect the  -12v to 5, the +12v to 12,   (the +12 is only logic I think, the pa supply is the +10v)

and then switch the +10v to 7/8/15 at the same time as logic 1 on pin 4?

Would that result in magic smoke being released?


Ben


Re: Rotator question

Reg Woolley
 

I had a spid much the same issue. If it's not true vertical it won't turn.  In the end I put a g1000 in. Now turns just fine.



Reg G8VHI


-------- Original message --------
From: Ian White <gm3sek@...>
Date: 13/12/2019 09:56 (GMT+00:00)
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Rotator question

Hello John

Pot replacement is not difficult, if you mount the rotator on washers as Conrad describes.

Unlike the Yaesu and other rotators, the PST rotators don't allow any rocking movement or side play at all as the mast turns. If the base plate in your head unit is even slightly tilted (which many are) you may need four different stacks of washers underneath the rotator to get it accurately levelled.

The pot is a standard Vishay/Spectrol part (RS part # 850-9855) except that the shaft needs to be cross drilled for the drive pin. Do get the identical part with the plastic shaft because it's a very tight fit into the bottom end of the rotator shaft, and that coupling desperately needs the tiny bit of extra flexibility.

For the last replacement - still only the second time in about 10 years - I reamed out the hole in  the rotator shaft to give a slightly looser fit, and smeared the pot shaft and cross pin with non-corroding silicone sealant before assembling. When the silicone has set to rubber, it makes a much better flexible coupling.

Unless the design has changed recently, the drip shield that protects the top bearing is ineffective when the tower is luffed over. Following a tip from GW8IZR, I made up a kind of giant Terry clip which pops on over the drip shield and covers the gap.

73 from Ian GM3SEK

On 12/12/2019 13:41, John Lemay wrote:
All

Many thanks to those of you who have taken the trouble to reply with your
rotator suggestions. I will sit and ponder on the information received, with
a plan to make some changes when the winter is over. No need to hurry, my
rotator isn't broken, and swapping out for a different model will be a lot
more than a five minute job !

Just one follow-up question: I can see that Prosistel is quite popular,
despite some issues with water ingress and potentiometer failure - so how
easy is the pot replacement ?

Thanks again

John G4ZTR

-----Original Message-----
From: John Lemay [mailto:john@...] 
Sent: 10 December 2019 19:16
To: UKMicrowaves@groups.io
Subject: Rotator question

'Evening all

What rotator do you use at home for the microwave bands ?

I have a Yaesu G-1000 here. It's man enough for my couple of dishes (2m and
1m) and a small yagi, but it has a backlash of about 1 degree. That's not a
lot of help when my 3cms dish has a 3dB beam-width of around 2 degrees !

Whatever I get, if I do change, will have to fit a standard Versatower head
unit.

Most makers don't specify the backlash, but I'm expecting those rotators
which use a worm gear off the motor will be better ?

A cue for tales of rotator woe perhaps ........

TIA

John G4ZTR




Re: Rotator question

Ian White
 

Hello John

Pot replacement is not difficult, if you mount the rotator on washers as Conrad describes.

Unlike the Yaesu and other rotators, the PST rotators don't allow any rocking movement or side play at all as the mast turns. If the base plate in your head unit is even slightly tilted (which many are) you may need four different stacks of washers underneath the rotator to get it accurately levelled.

The pot is a standard Vishay/Spectrol part (RS part # 850-9855) except that the shaft needs to be cross drilled for the drive pin. Do get the identical part with the plastic shaft because it's a very tight fit into the bottom end of the rotator shaft, and that coupling desperately needs the tiny bit of extra flexibility.

For the last replacement - still only the second time in about 10 years - I reamed out the hole in  the rotator shaft to give a slightly looser fit, and smeared the pot shaft and cross pin with non-corroding silicone sealant before assembling. When the silicone has set to rubber, it makes a much better flexible coupling.

Unless the design has changed recently, the drip shield that protects the top bearing is ineffective when the tower is luffed over. Following a tip from GW8IZR, I made up a kind of giant Terry clip which pops on over the drip shield and covers the gap.

73 from Ian GM3SEK

On 12/12/2019 13:41, John Lemay wrote:

All

Many thanks to those of you who have taken the trouble to reply with your
rotator suggestions. I will sit and ponder on the information received, with
a plan to make some changes when the winter is over. No need to hurry, my
rotator isn't broken, and swapping out for a different model will be a lot
more than a five minute job !

Just one follow-up question: I can see that Prosistel is quite popular,
despite some issues with water ingress and potentiometer failure - so how
easy is the pot replacement ?

Thanks again

John G4ZTR

-----Original Message-----
From: John Lemay [mailto:john@...] 
Sent: 10 December 2019 19:16
To: UKMicrowaves@groups.io
Subject: Rotator question

'Evening all

What rotator do you use at home for the microwave bands ?

I have a Yaesu G-1000 here. It's man enough for my couple of dishes (2m and
1m) and a small yagi, but it has a backlash of about 1 degree. That's not a
lot of help when my 3cms dish has a 3dB beam-width of around 2 degrees !

Whatever I get, if I do change, will have to fit a standard Versatower head
unit.

Most makers don't specify the backlash, but I'm expecting those rotators
which use a worm gear off the motor will be better ?

A cue for tales of rotator woe perhaps ........

TIA

John G4ZTR




Réf. : Re: [UKMicrowaves] Toshiba BA2076B amplifier for 24GHz ?

F1CHF
 

may be this jpeg will help you
thanks to Eric GHB
Francois F1CHF
 
 
 
 
 
-------Message original-------
 
De : Andy
Date : 12/12/2019 21:38:22
Sujet : Re: [UKMicrowaves] Toshiba BA2076B amplifier for 24GHz ?
 
I knew I had one somewhere.... I have a Toshiba BA2075B which I bought a while back but I very much doubt I'll be able to make use of it any time soon. It's more inband than a 2076B.
 
Contact me off list if you are interested.
 
Andy
MM0FMF
 
 
 

Re: Ionica Power amps

Andy G4JNT
 

A complete system ought to monitor the voltages via A/D converters and only allow the PA to go into Tx when they are in range
You shouldn't be switching on with the Tx is enabled  - so that delay from the DC-DC should never occur in operation.  Again a properly managed control can ensure this.
 


On Thu, 12 Dec 2019 at 18:26, John Quarmby via Groups.Io <g3xdy=btinternet.com@groups.io> wrote:

I have used this circuit for both Mikom and Ionica amps. The Ionica amp will take a fair bit of current if the -ve rail is absent but the dissipation is limited because there is only 1.2V on the drains of the devices. The LT1093 or similar 10V regulator will current limit so no damage results, but the voltage regulator will get very hot if left in that state (they reduce output current to keep the junction temperature within limits as the case temp goes up). Using a DC-DC converter generating the -ve rail from +13.8V DC in I see a current surge on switch on until the -ve bias starts to establish itself, its enough to cause some power supplies to go into fold back if they aren't rated for >10A output.

73

John G3XDY

On 12/12/2019 11:16, Andy G4JNT wrote:
Don't forget this well-known circuit is you're using a +V regulator with the same connections as the LM317 type.   
IIRC this actual circuit was used here for a Mikron or Ionica, (possibly both) power amplifier


This -Ve bias interlock circuit has actually been used in real satellites, and I don't mean amateur ones.




On Thu, 12 Dec 2019 at 11:05, Paul G8KFW <paul@...> wrote:

Hi

A problem when making a relay slow to operate, might be that if the external neg ve power is lost the relay might be slow to release  

 

Regards Paul


From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of militaryoperator via Groups.Io
Sent: 12 December 2019 09:24
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Ionica Power amps

 

No. I don't mean the ground line! 

I mean the -12 Volts supply!

You need an electronic sequencer that detects that the the -12 is present.... Waits a quarter of a second ish THEN applies the plus 12v supply. 

Such as 

Or in the simplest terms two switches 

 in the + and - 12v supplies and use your brains to make sure you click the -12 switch on BEFORE the +12 switch.

73 John

---------------------------

 

That's what my cct does John. The relay is between neg ( -12) and ground, so, on switch on, the neg goes to amp and relay, the relay then turns on the pos to the amp. 

You could add an R and C to delay the relay slightly.

I've added the ground line for clarity.

 

cheers, Ben.

 

 

amp.jpg

 


--
Paul Bicknell G8KFW   South Coast UK

Re: Toshiba BA2076B amplifier for 24GHz ?

Andy
 

I knew I had one somewhere.... I have a Toshiba BA2075B which I bought a while back but I very much doubt I'll be able to make use of it any time soon. It's more inband than a 2076B.

Contact me off list if you are interested.

Andy
MM0FMF

Re: Ionica Power amps

John Quarmby
 

I have used this circuit for both Mikom and Ionica amps. The Ionica amp will take a fair bit of current if the -ve rail is absent but the dissipation is limited because there is only 1.2V on the drains of the devices. The LT1093 or similar 10V regulator will current limit so no damage results, but the voltage regulator will get very hot if left in that state (they reduce output current to keep the junction temperature within limits as the case temp goes up). Using a DC-DC converter generating the -ve rail from +13.8V DC in I see a current surge on switch on until the -ve bias starts to establish itself, its enough to cause some power supplies to go into fold back if they aren't rated for >10A output.

73

John G3XDY

On 12/12/2019 11:16, Andy G4JNT wrote:
Don't forget this well-known circuit is you're using a +V regulator with the same connections as the LM317 type.   
IIRC this actual circuit was used here for a Mikron or Ionica, (possibly both) power amplifier


This -Ve bias interlock circuit has actually been used in real satellites, and I don't mean amateur ones.




On Thu, 12 Dec 2019 at 11:05, Paul G8KFW <paul@...> wrote:

Hi

A problem when making a relay slow to operate, might be that if the external neg ve power is lost the relay might be slow to release  

 

Regards Paul


From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of militaryoperator via Groups.Io
Sent: 12 December 2019 09:24
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Ionica Power amps

 

No. I don't mean the ground line! 

I mean the -12 Volts supply!

You need an electronic sequencer that detects that the the -12 is present.... Waits a quarter of a second ish THEN applies the plus 12v supply. 

Such as 

Or in the simplest terms two switches 

 in the + and - 12v supplies and use your brains to make sure you click the -12 switch on BEFORE the +12 switch.

73 John

---------------------------

 

That's what my cct does John. The relay is between neg ( -12) and ground, so, on switch on, the neg goes to amp and relay, the relay then turns on the pos to the amp. 

You could add an R and C to delay the relay slightly.

I've added the ground line for clarity.

 

cheers, Ben.

 

 

amp.jpg

 


--
Paul Bicknell G8KFW   South Coast UK

Re: Rotator question

Conrad, PA5Y
 

Hello John, provided you can easily get the whole rotator out of the rotator cage by lifting the stub mast then its quite easy. The pot sits in a void in the bottom of the  bell. These links will make it clear:



Make it so that you can slide and lock the stub mast some how. New PST61Ds come with a skirt over the output shaft and a small breathe hole. Place the rotator on 2 thick washers so there is a gap for condensed water to escape. If you want to reduce pot problems add a resistor dissipating 4-5W into the chamber and have a 2.5mm hole in the base cover plate. 

That will do it.

73

Conrad PA5Y


From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of John Lemay via Groups.Io <john@...>
Sent: 12 December 2019 14:41
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Rotator question
 
All

Many thanks to those of you who have taken the trouble to reply with your
rotator suggestions. I will sit and ponder on the information received, with
a plan to make some changes when the winter is over. No need to hurry, my
rotator isn't broken, and swapping out for a different model will be a lot
more than a five minute job !

Just one follow-up question: I can see that Prosistel is quite popular,
despite some issues with water ingress and potentiometer failure - so how
easy is the pot replacement ?

Thanks again

John G4ZTR

-----Original Message-----
From: John Lemay [mailto:john@...]
Sent: 10 December 2019 19:16
To: UKMicrowaves@groups.io
Subject: Rotator question

'Evening all

What rotator do you use at home for the microwave bands ?

I have a Yaesu G-1000 here. It's man enough for my couple of dishes (2m and
1m) and a small yagi, but it has a backlash of about 1 degree. That's not a
lot of help when my 3cms dish has a 3dB beam-width of around 2 degrees !

Whatever I get, if I do change, will have to fit a standard Versatower head
unit.

Most makers don't specify the backlash, but I'm expecting those rotators
which use a worm gear off the motor will be better ?

A cue for tales of rotator woe perhaps ........

TIA

John G4ZTR





Re: Rotator question

John Lemay
 

All

Many thanks to those of you who have taken the trouble to reply with your
rotator suggestions. I will sit and ponder on the information received, with
a plan to make some changes when the winter is over. No need to hurry, my
rotator isn't broken, and swapping out for a different model will be a lot
more than a five minute job !

Just one follow-up question: I can see that Prosistel is quite popular,
despite some issues with water ingress and potentiometer failure - so how
easy is the pot replacement ?

Thanks again

John G4ZTR

-----Original Message-----
From: John Lemay [mailto:john@...]
Sent: 10 December 2019 19:16
To: UKMicrowaves@groups.io
Subject: Rotator question

'Evening all

What rotator do you use at home for the microwave bands ?

I have a Yaesu G-1000 here. It's man enough for my couple of dishes (2m and
1m) and a small yagi, but it has a backlash of about 1 degree. That's not a
lot of help when my 3cms dish has a 3dB beam-width of around 2 degrees !

Whatever I get, if I do change, will have to fit a standard Versatower head
unit.

Most makers don't specify the backlash, but I'm expecting those rotators
which use a worm gear off the motor will be better ?

A cue for tales of rotator woe perhaps ........

TIA

John G4ZTR