On Wednesday, November 8, 2023 at 1:12:11 PM UTC-5, bitrex wrote:
> On 11/8/2023 11:47 AM, Fred Bloggs wrote: 
> > On Wednesday, November 8, 2023 at 11:11:40 AM UTC-5, bitrex wrote: 
> >> On 11/7/2023 5:42 PM, Simon S Aysdie wrote: 
> >>> On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote: 
> >>>> How is "directivity" defined for these Minicircuits gain blocks? 
> >>>> Datasheet here: 
> >>>> 
> >>>> <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf> 
> >>>> 
> >>>> Across the bandwidth of interest I'm measuring S21 as about 20-something 
> >>>> dB give or take a dB which seems fine, S12 is at -40. 
> >>>> 
> >>>> If "directivity" in this context is just S12 then that seems within spec 
> >>>> but if it's |S21 - S12| then something seems wrong with my setup and/or 
> >>>> the amp. 
> >>>> 
> >>>> Doing the measurements on a (unfortunately not my personal home-lab 
> >>>> machine!) Keysight 5080. 
> >>> 
> >>> They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you noted. 
> >>> 
> >>> Example: 
> >>> For "unit 1" and at 100 MHz, forward gain is +24.47859 dB. 
> >>> For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB. 
> >>> 
> >>> Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB) 
> >>> 
> >>> !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON) 
> >>> # Hz S dB R 50 
> >>> 100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002 
> >> Thanks Simon, yes that seems right, this amp was bang on within spec 
> >> otherwise so I'd have been surprised if it was way off there. 
> >> 
> >> They're nice lil modules, I didn't have this purpose in mind but I 
> >> wonder if they make a LNA suitable to replace the shit ass front end on 
> >> my DTV antenna, I live in a fringe area so reception varies by the day. 
> >> and I'm in a condo so mounting stuff outdoors not really feasible 
> > 
> > Your reception is probably being degraded by suboptimal antenna pointing, the sun, and unpredictable multi-path signal impingement [ coastal is littoral causes no end of propagation anomalies ]. It doesn't cost the manufacturer anything to provide a high performance front end amplifier
> It doesn't?
> all of which intended for satellite reception are LN-A's. The 
> customers pay for everything, do you think it's wise then for them to 
> provide junk performance parts making customers into ex-customers?
> Could apply the same argument to many other industries...and conclude 
> all products are high-quality because otherwise the manufacturer might 
> lose customers. 

The business is going to provide the best part suited for the application and price range.  It doesn't take state-of-the-art. 

Your reception is problematic because of the location and other factors. Nothing by way of more expensive parts is going to fix it.


> 
> Hey, I have a cool idea, I'll see if I can put it on the 5080 next time 
> I have a chance and see how it compares to a Minicircuits gain block for 
> similar bandwidth, I think I can get a hold of one..

On 2023-11-07 17:45, Simon S Aysdie wrote:
> On Tuesday, November 7, 2023 at 2:42:48 PM UTC-8, Simon S Aysdie wrote:
>> On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
>>> How is "directivity" defined for these Minicircuits gain blocks?
>>> Datasheet here:
>>>
>>> <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>
>>>
>>> Across the bandwidth of interest I'm measuring S21 as about 20-something
>>> dB give or take a dB which seems fine, S12 is at -40.
>>>
>>> If "directivity" in this context is just S12 then that seems within spec
>>> but if it's |S21 - S12| then something seems wrong with my setup and/or
>>> the amp.
>>>
>>> Doing the measurements on a (unfortunately not my personal home-lab
>>> machine!) Keysight 5080.
>> They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you noted.
>>
>> Example:
>> For "unit 1" and at 100 MHz, forward gain is +24.47859 dB.
>> For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB.
>>
>> Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)
>>
>> !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON)
>> # Hz S dB R 50
>> 100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002
> 
> 
> I should say:
> D = -|S12| (dB)
> 

(Supernews doesn't seem to be registering my 3 PM EST reply just 
now--apologies for duplication if it shows up eventually.)

It makes no sense to take the absolute value of a quantity expressed in 
decibels--that's saying that there's no difference between, say, a 100X 
voltage amp (+40 dB) and a 40-dB attenuator (-40 dB).

The directivity is just |S12 * S21|,  i.e. the effects at one port of a 
short-circuit load reflecting all of the signal backwards through the 
network. In decibels, it's

D = 20 log(|S12 * S21|).  Symmetrical. No big mystery.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On 11/8/2023 5:02 PM, upsidedown@downunder.com wrote:
> On Wed, 8 Nov 2023 11:11:31 -0500, bitrex <user@example.net> wrote:
> 
>> They're nice lil modules, I didn't have this purpose in mind but I
>> wonder if they make a LNA suitable to replace the shit ass front end on
>> my DTV antenna, I live in a fringe area so reception varies by the day.
>> and I'm in a condo so mounting stuff outdoors not really feasible
> 
> That ZFL-500 is not very suitable as antenna amplifier for DTV. First
> of all it is quite noisy, noise figure NF = 4.2 dB (typical). These
> days a good antenna amplifier the NF should be below 3 dB. That
> amplifier is specified only up to 500 MHz, thus most UHF channels are
> out of range. However, it might still work since the specs are good at
> 500 MHz, wonder why the specs ends at 500 MHz.

Yeah it has gain for days. S21 is above 20dB well past 1 GHz.

> An antenna amplifier should be installed _at_ the antenna, thus the
> cable between amplifier and DTV receiver can be long.
> 
> You seem to suffer from tropospheric fading and the signal nulls can
> be quite deep and the signal is still momentary lost no matter what
> antenna amplifier you use. Only a proper outdoor antenna will really
> help.

I'll see if high pressure systems seem to make it better...atm with a 
planar antenna and associated amp I'm getting a station with a purported 
field strength of -70 dBm at 36 miles no problem if I kinda point it in 
that direction, but a station at 16 miles -50 dBm doesn't come in at all 
/shrug

On Wed, 8 Nov 2023 11:11:31 -0500, bitrex <user@example.net> wrote:

>They're nice lil modules, I didn't have this purpose in mind but I 
>wonder if they make a LNA suitable to replace the shit ass front end on 
>my DTV antenna, I live in a fringe area so reception varies by the day. 
>and I'm in a condo so mounting stuff outdoors not really feasible

That ZFL-500 is not very suitable as antenna amplifier for DTV. First
of all it is quite noisy, noise figure NF = 4.2 dB (typical). These
days a good antenna amplifier the NF should be below 3 dB. That
amplifier is specified only up to 500 MHz, thus most UHF channels are
out of range. However, it might still work since the specs are good at
500 MHz, wonder why the specs ends at 500 MHz.

An antenna amplifier should be installed _at_ the antenna, thus the
cable between amplifier and DTV receiver can be long.

You seem to suffer from tropospheric fading and the signal nulls can
be quite deep and the signal is still momentary lost no matter what
antenna amplifier you use. Only a proper outdoor antenna will really
help.

On 2023-11-07 17:42, Simon S Aysdie wrote:
> On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
>> How is "directivity" defined for these Minicircuits gain blocks?
>> Datasheet here:
>>
>> <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>
>>
>> Across the bandwidth of interest I'm measuring S21 as about 20-something
>> dB give or take a dB which seems fine, S12 is at -40.
>>
>> If "directivity" in this context is just S12 then that seems within spec
>> but if it's |S21 - S12| then something seems wrong with my setup and/or
>> the amp.
>>
>> Doing the measurements on a (unfortunately not my personal home-lab
>> machine!) Keysight 5080.
> 
> They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity.  By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you noted.
> 
> Example:
> For "unit 1" and at 100 MHz, forward gain is +24.47859 dB.
> For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB.
> 
> Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)
> 
> !Freq	S11:SOLT2(ON)	S21:SOLT2(ON)	S12:SOLT2(ON)	S22:SOLT2(ON)
> # Hz S dB R 50
> 100000000	-3.318152e+001	-2.120138e+001	2.447859e+001	-1.975411e+001	-3.836183e+001	-1.134106e+001	-2.672768e+001	-1.570933e+002
> 

It isn't the absolute value in decibels.  The directivity is just the 
magnitude of S21*S12.  Otherwise you get the wrong answer for attenuators.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On 11/8/2023 11:47 AM, Fred Bloggs wrote:
> On Wednesday, November 8, 2023 at 11:11:40 AM UTC-5, bitrex wrote:
>> On 11/7/2023 5:42 PM, Simon S Aysdie wrote:
>>> On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
>>>> How is "directivity" defined for these Minicircuits gain blocks?
>>>> Datasheet here:
>>>>
>>>> <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>
>>>>
>>>> Across the bandwidth of interest I'm measuring S21 as about 20-something
>>>> dB give or take a dB which seems fine, S12 is at -40.
>>>>
>>>> If "directivity" in this context is just S12 then that seems within spec
>>>> but if it's |S21 - S12| then something seems wrong with my setup and/or
>>>> the amp.
>>>>
>>>> Doing the measurements on a (unfortunately not my personal home-lab
>>>> machine!) Keysight 5080.
>>>
>>> They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you noted.
>>>
>>> Example:
>>> For "unit 1" and at 100 MHz, forward gain is +24.47859 dB.
>>> For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB.
>>>
>>> Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)
>>>
>>> !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON)
>>> # Hz S dB R 50
>>> 100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002
>> Thanks Simon, yes that seems right, this amp was bang on within spec
>> otherwise so I'd have been surprised if it was way off there.
>>
>> They're nice lil modules, I didn't have this purpose in mind but I
>> wonder if they make a LNA suitable to replace the shit ass front end on
>> my DTV antenna, I live in a fringe area so reception varies by the day.
>> and I'm in a condo so mounting stuff outdoors not really feasible
> 
> Your reception is probably being degraded by suboptimal antenna pointing, the sun, and unpredictable multi-path signal impingement [ coastal is littoral causes no end of propagation anomalies ]. It doesn't cost the manufacturer anything to provide a high performance front end amplifier

It doesn't?

  all of which intended for satellite reception are LN-A's. The 
customers pay for everything, do you think it's wise then for them to 
provide junk performance parts making customers into ex-customers?

Could apply the same argument to many other industries...and conclude 
all products are high-quality because otherwise the manufacturer might 
lose customers.

Hey, I have a cool idea, I'll see if I can put it on the 5080 next time 
I have a chance and see how it compares to a Minicircuits gain block for 
similar bandwidth, I think I can get a hold of one..

On Wednesday, November 8, 2023 at 11:11:40 AM UTC-5, bitrex wrote:
> On 11/7/2023 5:42 PM, Simon S Aysdie wrote: 
> > On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote: 
> >> How is "directivity" defined for these Minicircuits gain blocks? 
> >> Datasheet here: 
> >> 
> >> <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf> 
> >> 
> >> Across the bandwidth of interest I'm measuring S21 as about 20-something 
> >> dB give or take a dB which seems fine, S12 is at -40. 
> >> 
> >> If "directivity" in this context is just S12 then that seems within spec 
> >> but if it's |S21 - S12| then something seems wrong with my setup and/or 
> >> the amp. 
> >> 
> >> Doing the measurements on a (unfortunately not my personal home-lab 
> >> machine!) Keysight 5080. 
> > 
> > They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you noted. 
> > 
> > Example: 
> > For "unit 1" and at 100 MHz, forward gain is +24.47859 dB. 
> > For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB. 
> > 
> > Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB) 
> > 
> > !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON) 
> > # Hz S dB R 50 
> > 100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002
> Thanks Simon, yes that seems right, this amp was bang on within spec 
> otherwise so I'd have been surprised if it was way off there. 
> 
> They're nice lil modules, I didn't have this purpose in mind but I 
> wonder if they make a LNA suitable to replace the shit ass front end on 
> my DTV antenna, I live in a fringe area so reception varies by the day. 
> and I'm in a condo so mounting stuff outdoors not really feasible

Your reception is probably being degraded by suboptimal antenna pointing, the sun, and unpredictable multi-path signal impingement [ coastal is littoral causes no end of propagation anomalies ]. It doesn't cost the manufacturer anything to provide a high performance front end amplifier- all of which intended for satellite reception are LN-A's. The customers pay for everything, do you think it's wise then for them to provide junk performance parts making customers into ex-customers?

On 11/7/2023 5:42 PM, Simon S Aysdie wrote:
> On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
>> How is "directivity" defined for these Minicircuits gain blocks?
>> Datasheet here:
>>
>> <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf>
>>
>> Across the bandwidth of interest I'm measuring S21 as about 20-something
>> dB give or take a dB which seems fine, S12 is at -40.
>>
>> If "directivity" in this context is just S12 then that seems within spec
>> but if it's |S21 - S12| then something seems wrong with my setup and/or
>> the amp.
>>
>> Doing the measurements on a (unfortunately not my personal home-lab
>> machine!) Keysight 5080.
> 
> They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity.  By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you noted.
> 
> Example:
> For "unit 1" and at 100 MHz, forward gain is +24.47859 dB.
> For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB.
> 
> Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)
> 
> !Freq	S11:SOLT2(ON)	S21:SOLT2(ON)	S12:SOLT2(ON)	S22:SOLT2(ON)
> # Hz S dB R 50
> 100000000	-3.318152e+001	-2.120138e+001	2.447859e+001	-1.975411e+001	-3.836183e+001	-1.134106e+001	-2.672768e+001	-1.570933e+002

Thanks Simon, yes that seems right, this amp was bang on within spec 
otherwise so I'd have been surprised if it was way off there.

They're nice lil modules, I didn't have this purpose in mind but I 
wonder if they make a LNA suitable to replace the shit ass front end on 
my DTV antenna, I live in a fringe area so reception varies by the day. 
and I'm in a condo so mounting stuff outdoors not really feasible

On Tuesday, November 7, 2023 at 2:42:48 PM UTC-8, Simon S Aysdie wrote:
> On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote: 
> > How is "directivity" defined for these Minicircuits gain blocks? 
> > Datasheet here: 
> > 
> > <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf> 
> > 
> > Across the bandwidth of interest I'm measuring S21 as about 20-something 
> > dB give or take a dB which seems fine, S12 is at -40. 
> > 
> > If "directivity" in this context is just S12 then that seems within spec 
> > but if it's |S21 - S12| then something seems wrong with my setup and/or 
> > the amp. 
> > 
> > Doing the measurements on a (unfortunately not my personal home-lab 
> > machine!) Keysight 5080.
> They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity. By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you noted. 
> 
> Example: 
> For "unit 1" and at 100 MHz, forward gain is +24.47859 dB. 
> For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB. 
> 
> Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB) 
> 
> !Freq S11:SOLT2(ON) S21:SOLT2(ON) S12:SOLT2(ON) S22:SOLT2(ON) 
> # Hz S dB R 50 
> 100000000 -3.318152e+001 -2.120138e+001 2.447859e+001 -1.975411e+001 -3.836183e+001 -1.134106e+001 -2.672768e+001 -1.570933e+002


I should say:
D = -|S12| (dB) 

On Saturday, November 4, 2023 at 1:55:09 PM UTC-7, bitrex wrote:
> How is "directivity" defined for these Minicircuits gain blocks? 
> Datasheet here: 
> 
> <https://www.mouser.com/datasheet/2/1030/ZFL_500_2b-3305829.pdf> 
> 
> Across the bandwidth of interest I'm measuring S21 as about 20-something 
> dB give or take a dB which seems fine, S12 is at -40. 
> 
> If "directivity" in this context is just S12 then that seems within spec 
> but if it's |S21 - S12| then something seems wrong with my setup and/or 
> the amp. 
> 
> Doing the measurements on a (unfortunately not my personal home-lab 
> machine!) Keysight 5080.

They give S-params for 2 units. Conveniently, they are in dB/angle. The table just says 38 dB, more or less for directivity.  By a quick look at the S-params and comparing to the datasheet table, I think they are just saying D = |S12| (dB), which you noted. 

Example:
For "unit 1" and at 100 MHz, forward gain is +24.47859 dB. 
For "unit 1" and at 100 MHz, reverse gain is -38.36183 dB. 

Because the "directivity" looks to be about same as |S12|, it is safe to say they mean D = |S12| (dB)

!Freq	S11:SOLT2(ON)	S21:SOLT2(ON)	S12:SOLT2(ON)	S22:SOLT2(ON)
# Hz S dB R 50
100000000	-3.318152e+001	-2.120138e+001	2.447859e+001	-1.975411e+001	-3.836183e+001	-1.134106e+001	-2.672768e+001	-1.570933e+002