Friday, 30 November 2018

Vector Signal Analysis: Agilent 89600 VSA software and E4406A Vector Signal Analyser

Vector Signal Analysis: Agilent 89600 VSA software and E4406A Vector Signal Analyser

A very powerful test equipment resource is available with the older versions of the Agilent 89600 Vector Signal Analysis software combined with the E4406A Signal Analyser hardware for DATV and other amateur radio.





Version 12 of the Agilent 89600 software is the last that will work with the E4406A hardware. It, and earlier versions, can be accessed at: http://www.home.agilent.com/agilent/editorial.jspx?cc=TW&lc=cht&ckey=1303376&nid=-34704.626687.00&id=1303376

or
https://www.keysight.com/main/software.jspx?cc=AU&lc=eng&ckey=1303376&nid=-32400.350722.02&id=1303376

The last version of the 89600 software that will work with the



Registry edits for version 10 to 12 to work with E4406A
https://community.keysight.com/thread/5127


For 89601B versions
https://www.keysight.com/main/software.jspx?cc=AU&lc=eng&nid=-32806.0.02&id=2013472&pageMode=PV

Firmware updates E4406A and others
https://www.keysight.com/main/editorial.jspx?cc=AU&lc=eng&ckey=1362070&nid=-32400.350722.02&id=1362070&ml=eng


Windows XP and VXI supported to version 17.22.

Support for hardware and Windows versions is detailed in the updates to 89601A/B See previous versions download page above.
















Monday, 27 August 2018

Variable-length phasing cables for tuning repeater duplexers: Part 2, Using the cable

Variable-length phasing cables for tuning repeater duplexers: Part 2, Using the cable (draft)

Introduction

In Part 1, a variable-length phasing cable for use in determining duplexer cable lengths, using M/F SMA connectors to vary the length is discussed.

In Part 2, this post, I will cover the use of the variable-length phasing cable in more detail.

say more??

The basic process

The basic process of using a variable-length phasing cable to tune a six cavity duplexer:

1/ Tune each cavity to frequency.

2/ Connect the three cavities with two same length adjustable phasing cables of approximately the right length

3/ Using a spectrum analyser and tracking generator or a vector network analyser (VNA), take out or insert SMA connectors in both cables until the desired response is achieved.

4/ Using a Tee connector between the ports of the instrument, measure the resonate frequency of one of the correct length variable cables as a quarter wave stub.

5/ Cut a length of cable a little longer than desired, attach one connector, connect to Tee and measure the resonate length. Cut the cable to that of the variable length cable.

6/ Attach the second connector and check that the resonate frequency is the same as the variable-length cable. Make a second phasing cable to the same length.

7/ Attach both new phasing cables to the duplexer and check the desired response is achieved.

8/ Repeat for the other side of the duplexer.


1/ Tune each cavity to frequency.

??

2/ Connect the three cavities with two same length adjustable phasing cables of approximately the right length

??

3/ Take out or insert SMA connectors in both cables until the desired response is achieved.

??

4/ Measure the resonate frequency of one of the correct length variable cables as a quarter wave stub.

??

5/ Cut a new cable of the same length. 

??

6/ Complete cable and check length.

??

7/ Attach both new phasing cables to the duplexer and check the desired response is achieved (repeat 2&3).

??

8/ Repeat for the other side of the duplexer.

??

Discussion

??

Conclusion


Sunday, 26 August 2018

Variable-length phasing cables for tuning repeater duplexers: Part 1, Construction of the cable

Variable-length phasing cables for tuning repeater duplexers: Part 1, Construction of the cable

Introduction

A variable-length phasing cable for use in determining duplexer cable lengths, using M/F SMA connectors to vary the length is proposed. It is a cheaper alternative to a set of phasing cables with a 10mm (5mm?) length increment.

This post describes the concept and how it can be replicated. A simple idea, but some frustration in execution. The basic process of using the variable-length cables is outlined.

The next post will cover the use of the variable length cables and include screenshots from instruments and photos.

The problem: determining cable lengths for inter-connecting duplexer cavities

Determining cable lengths for inter-connecting duplexer cavities is a perennial topic. Notionally, they are a quarter wavelength or odd multiple, allowing for coax velocity factor, but in practice that is a starting point.

My understanding is that commercially, a set of incremental length cables are used to find the correct lengths. Unfortunately, most people don't have such a set of cables.

An additional problem for a six cavity duplexer (3 RX, 2 TX) is that the two cavity inter-connecting cables interact, so both cables need to be varied in length at once to get a good filter response.

A solution: a variable length of coax!

A solution is a variable length of coax. My first attempt was to use M/F N-type connectors with short lengths of cable to change the length in 25mm increments. This was too coarse, giving a 10 MHz or more change in resonance as a quarter wave stub.

My second attempt was to incorporate a home-made sliding trombone joint, made of rolled copper shim for the outer, and small brass tubes for the inner. This gave a continuously variable length of 25mm to fit the gap using M/F N connectors. It works but is too stiff and delicate for practical use.

A variable length of coax using M/F N connectors and a home-made telescopic joint

My third attempt, and the one pursued, was to use SMA M/F connectors to change the cable length. The thin cable is flexible and the SMA connectors give an increment of about 10mm. Effectively, the increment is 5mm as the cable may be too long or too short, adding or removing a connector, where the optimum is half a connector length.

A variable length of coax using M/F SMA and N connectors


The variable length phasing cables are made up from M/F SMA connectors, N to SMA adaptors and SMA M/M pigtail cables. I used cheap Chinese parts to keep costs down; about $2 each. To make one general purpose cable, I suggest 10 M/F SMA connectors and two 100 and 200mm pigtail cables, plus the two SMA-N adapters. Double to make two cables as two cables are needed.

Purchasing the M/F SMA connectors was problematic as they are fairly scarce. More numerous are reverse polarity (RP) connectors. If the description has RP in it, it is the wrong type!

https://www.ebay.com/itm/SMA-adapter-SMA-Plug-male-to-SMA-Jack-female-RF-Coax-Adapter-connector-straight/151338805239?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

The ordinary purpose of M/F connectors was a mystery to me as the seem to achieve nothing. It seems their main use is as connector protectors on instruments. It seemed such a good idea that I used a few on my instruments. Connectors are only good for about 400 connection cycles, plus the problem of cross threads.

A M/F SMA connector, showing pin. There is a hole in the other end. Most on eBay are reverse polarity, RP types.
Subsequent to building the N type telescopic joint, I found via Google, that such joints are commercially available as an SMA adjustable phase trimmer. Oh to re-invent the wheel, again! But shows my thinking is on track. The only problem with such devices is the cost, about $200 and two are needed. Such a device could be used to give continuous adjustment for the 10 mm gap between the M/F SMA connectors, as per my telescopic N-type joint. However, I have not tried this device and don't know if it is the most suitable; make your own enquires before purchasing!

https://www.pasternack.com/adjustable-phase-trimmer-18-ghz-sma-10-deg-per-ghz-pe8203-p.aspx

SMA adjustable phase trimmer

Using variable length phasing cables

While the detailed procedure for using the cables will be covered in another blog post, with photos, the basic procedure to determine duplexer phasing cable lengths is as follows.

1/ Tune each cavity to frequency.

2/ Connect the three cavities with the two same-length adjustable cables, based on a calculation of a quater wave length (or odd multiple), taking into account both the velocity factor of the SMA cable and the length of connectors or Tee pieces on the cavities (assume the connectors are the same velocity factor as the cable). Roughly, 300mm for 2m using RG-214 between Tee connectors on cavities, 12mm less for N-type in-out sockets.

3/ Using a spectrum analyser and tracking generator or a vector network analyser (VNA), take out or insert SMA connectors in both cables until the desired response is achieved. Possibly (to be confirmed in next post), if the desired response is between an increment up or down in length, the desired length is half an SMA connector's effective length, about 5mm.

4/ Using a Tee connector between the ports of the instrument, measure the resonate frequency of one of the correct length variable cables as a quater wave stub. The frequency will be 10 MHz or so above the frequency of the cavity as to cavity connectors contribute to phasing cable length.

5/ Cut a length of cable a little longer than desiered, taking into account any difference with the SMA cable velocity factor. Attach one connector. Connect to Tee and measure the resonate length. Cut the length of the cable to increase the resonate frequency to that of the variable length cable (may need to allow a little for the second connector, to be confirmed, but will be small a couple of mm). If the length is between SMA connector increments, allow the 5mm or so (to be checked).

6/ Attach the second connector and check that the resonate frequency is the same as the variable-length cable. Make a second phasing cable to the same length.

7/ Attach both new phasing cables to the duplexer and check the desired response is achieved.

Conclusion

A variable-length phasing cable for use in determing duplexer cable lengths has been described, as an cheaper alternative to a set of phasing cables with a 10mm length increment. The cable uses M/F SMA connectors to vary the length.

The next post will cover the use of the variable length cables and include screen shots from instruments and photos.

Tuesday, 24 July 2018

3D printing or fabricated UHF filters


3D printing or fabricated UHF filters


Not crazy idea, being done with antennas. In Jan 2019 QST. Silver conductive paint.

Should work for filters.

Dimensional stability important with some narrow filters, less so with wideband filters.

https://antennatestlab.com/3dprinting


https://all3dp.com/1/creality-ender-3-3d-printer-review/







Settings
https://www.youtube.com/watch?v=umulfK775i0


https://ultimaker.com/en/products/ultimaker-cura-software


https://ultimaker.com/en/resources/50296-which-material-should-i-use


Silver coating/paint MG Chemicals Amazon.com
https://www.mektronics.com.au/mg-chemicals-super-shieldtm-silver-coated-copper-conductive-coating-ul-recognized-340g.html

Fabricated

Construct with soldered copper then coat with silver paint.


Copper and silver plating
https://bryancera.blogspot.com/2014/09/copper-electroplatingforming-3d-prints.html
https://www.riogrande.com/category/tools-and-equipment/plating
https://janekits.com.au/products/copper-mix-inc-cumac-4-ltrs/
http://www.vitec.com.au/shop-online/pat-coleby-minerals/copper-sulphate

https://www.finishing.com/111/72.shtml
https://www.eevblog.com/forum/manufacture/my-way-to-professional-prototype-at-home/25/
https://www.thinktink.com/stack/volumes/voliii/consumbl/cplatmix.htm
https://www.thinktink.com/faqs/cupltfaq/cupltf01.htm












HP AGILENT 8935 E6380A RF TEST SET


HP AGILENT 8935 E6380A RF TEST SET

Service Monitor for HF and 2 way radio. They all generate AM, FM and have a calibrated output signal generator, have 2 separate audio tone generators, have 2uV sensitive "off the air receivers" with antenna input, encode/decode standard tone (PL) (CTCSS), have sinad, distortion, S/N meters, receive AM, FM and SSB, have modulation / deviation meter, frequency error meters.





Overview and screens for HP 8935 E6380A
http://www.amtronix.com/e6380a.htm


Comparison with other HP test sets
http://www.amtronix.com/diff.htm



All manuals available through Keysight, just search E6380.

Sunday, 15 July 2018

Commercial low power UHF DVB-T pass-band/notch filter

Commercial  DVB-T pass-band/notch filters: What we can learn

Introduction

Low power, UHF and VHF DVB-T pass-band/notch filters are commercially available at relatively low cost, ~US$750 that seem suitable for DATV. They seem a good off the shelf solution.

By examining such filters, it seems possible to see how they might work, giving some insight into possible home-brew.

The filters have two notch filters, one for each side of the signal, as per my earlier posts, to notch the TX skirts.

In addition, they have cavity pass-band filters to take out artefacts further out. A manufacturer indicates that the pass filter is a combline, but the mechanical construction suggests cavity filters with openings between cavities for coupling.

It seems possible to separate the notch and band-pass filters. For wideband UHF, two notch cavities and a pass-band filter. For 2m, two notch cavities and a single pass cavity may suffice.

Low-pass filters are still needed for odd harmonics in addition to a DVB-T filter.

Commercial filters DVB-T (UHF and VHF)

The UHF first commercial filter seems to have five band-pass cavities and two notch cavities, one at either end. The input, notch and first pass resonator seem to share the same cavity, similarly for output. Three of the resonators are in individual cavities. On the top, RHS of the filter are the resonator tuning knobs.

 http://www.com-tech.it/products/cl-series-c/




From the response curves, the two sharp notches are evident to filter the skirts. This is similar to what I found in earlier posts on notch duplexers for DVB-T. However, one pair seems sufficient, something I have been working on, rather than 3 pairs in a duplexer.

How the notches work is not particularly evident. The connector has a loop coupling per the manufacturer's claim of DC to earth for lightning protection. There is a protrusion on the opposite side of the connector, the purpose of which is not evident. The notch and first pass-band resonator seem to be in the same cavity. Each resonator may be energised, one as a notch, the other as the first resonator of the pass-band filter.

The response shows the five minimums in SWR from the five cavities. The pass-band is shown without ripples, which seems a bit optimistic.

The response also shows the filter losses, less than 1 dB according to the specifications; quite remarkable!



The filter is meant to be a combline, presumably similar to the diagram from Piette 2010.


However, the cavities seem to have openings between them as the line of screws do not go all the way. It would seem to be similar to the band-pass filter from Piette 2010. It is not clear from the first drawing if there are screws to adjust coupling, but there seems to be another adjustment next to the resonator tuning.

From the mechanical design, it does not seem to be an inter-digital filter.


The filter is quite small,

Third harmonic?

Size Power


http://www.com-tech.it/products/cl-series-c/
http://www.com-tech.it/glossary/xline/
http://www.sira.mi.it/en/products/broadcasting/8/uhf-dtv-filters/287

http://www.microwavefilter.com/FCC_Repack.html
http://www.sira.mi.it  http://nintermedia.com/pdfs/tv/CTV-V-DVB-025.pdf

Homebrew DVB-T TX filter?



http://www.ocicom.com/index.php/amateur-radio/products/440-mhz-bandpass-filter
Bernard Piette 2010 VHF/UHF Filters and Multicouplers: Applications of Air Resonators










Wednesday, 11 July 2018

450 MHz CDMA duplexer tear down and analysis


450 MHz CDMA duplexer tear down and analysis- draft

Introduction


Why?

I am interested in how modern duplexers work. The club purchased a new 70cm duplexer, only 50 mm tall and not obvious how it worked, but they didn't want me opening it for a look!

I purchased a CDMA duplexer from Russia on the 450 MHz band on eBay. It was similar to the 70 cm one. I could get some idea how the UHF one works and some(?!) chance of re-tuning it for either a 70 cm DVB-T TV filter, 7 MHz bandpass, or as a 70 cm narrow pass band repeater duplexer (or both, as there are three chains of seven cavities in the device.

Unfortunately, I did not take photos of the duplexer's response before I opened it. However, it was a 6 MHz pass band, with steep skirts, and low pass in the 450 MHz band. I will do it when I put the top back on, but have probably disturbed the tuning. CDMA signals are 1.23 MHz wide, so it is unclear why the pass band is 6 MHz.

The outside, with a zillion screws out. The left three connectors are all SMA, the right are 7/16 DIN and N adaptors that I added.

The gizzards!

Click photo to see captions larger!!


It is a complex beast, requiring a very detailed examination to see all its features. Pore over the photo to see.

?? = I think!

The duplexer has three chains of cavity filters, RX (top), RX monitor (middle) and TX (bottom). RX has its own antenna. TX and RX monitor share an antenna, but are on different frequencies. Tx input is to left. The resonators use big capacitive hats to electrically shorten the resonator to one rack height, otherwise four rack high. The resonator adjustment screws are the larger screws.

The filters are pass band and low pass. The low pass comes from the capacitive tuning into the resonator??

The filter chains are pass-band, iris-coupled (port-tuned) filters that have a sharp cut off. The iris-coupling screws are the smaller screws. In addition to iris-coupling, both inductive (on lid) and capacitive inter-cavity coupling are used. I don't know why, presumably to get a sharper response (or impedence matching??). There are no notch filters, as are used in DVB-T filters, to get a very sharp cut at the edges of the pass band.

The input/output are either a separate smaller resonator with a gamma match?? coupling (left), or a conventional gamma match?? coupling direct to the main resonator (right).