CW/SSB roofing filter FT1000MP( Slovenian language-English abstract)

ABSTRACT

 

After INRAD FT1000MP roofing filter is no longer in a production I have decided to make my own roofing filter. Roofing filter attenuates and reduce IMD3 products and DSP has less bandwith to process. Unfortunately especially on CW, the INRAD 6 kHz wide roofing filter was not narrow and efficient enough for serious contest, so I decided to make my own  2 kHz SSB and  also CW 1,4kHz  wide roofing filter.

The same Roofing  Filter can be  with minor changes used for up conversion receivers  with first  intermediate frequency (IF)  between 60 in 75 Mhz  like :

 ICOM  IC : 756, 765, 775, 7400, 7410, 7700, 7850, 7851,9100

 Kenwood  TS : 450, 850,  870,  950

 Yaesu  FT :  450, 847, 897, 920, 950,1000MP, 1000D, 2000,9000

More informations in Slovenian language ( use Google translate) The photo's are self explanatory

INRAD je pred leti dobavljal roofing filtre za FT1000MP. Žal so bili ti filtri

zaradi svoje širine okrog 6 kHz za  resen CW contest  neučinkoviti. (slika 1). Inradov filter  je imel tudi sistemsko napako- ojačevalnik za filtrom je imel namreč za 3,5dB preveliko ojačenje ( VA3CR),kar je pomenilo za 10,5dB povečanja IMD3,  zato praktično ni bilo opaznega izboljšanja IMD3 na razmaku 2kHz.

Slika 1 :  Inrad roofing filter   FT 920( FT 1000MP)   6,1kHz /-6dB

S54X me je zaprosil,če mu na podlagi rezultatov roofinga FT 950 izdelam roofing za njegov FT 1000MP.

Ker je Rajko S54X pretežno aktiven na CW  sem kot kompromis, da je filter uporaben tudi na SSB izbral  pasovno širino 2kHz na -6dB (slika 2, 3 )

Slika 2,3 :  Roofing filter širine 2kHz /- 6dB

Izmerjene  karakteristike : Band 7 Mhz, 500HZ CW filter, spacing 2kHz,  AGC off, IPO

MDS -134dBM

RMDR(2 kHz) 91 dB

IMD3(2kHz) 86dB

IMD2 ( 14102kHz) 87dB

Bloking(100kHz) >140dB

 za primerjavo z "Sherwood Receiver test data"  se vidi, da je  IMD 3 izboljšanje za 17 dB  iz 69dB na 86dB  izboljšava napram Inrad roofingu pa za 15 dB, to je  iz 71dB na 86dB. S temi podatki se sprejemnik FT1000MP lahko uvršča med boljše tekmovalne postaje. Zanimivo bi bilo tudi zamenjati roofing v drugem sprejemniku FT 1000MP.

Sherwood Receiver test data  FT1000MP

Sherwood Receiver test data  FT1000MP + INRAD roofing filter

 

Slika 5: Priključitev roofing filtra v FT 1000MP

Slika 6:  Celotna slika vgradnje

Rajko S54X je vgrajen roofing filter  preizkusil v tekmovanju EUHFC 2020 ,kjer je v kategoriji LP solo FT 1000MP  napravil lep rezultat  838 zvez in je s spremenbo zelo zadovoljen.

Še boljši rezultat je Rajko S54X  s solo  FT1000MP dosegel v EU- DX 2021 Contestu

Shema filtra je enaka,kot sem jo objavil v reviji CQ ZRS 2018/1-2   Roofing filter za FT897D   ozr. je na mojem blogu  Roofing filter za FT 897D.

Filter sem konstruiral s pomočjo programa Dishal avtorja DJ6EV , impedančno pa sem filter prilagajal na 50 Ohmov s pomočjo programa AADE.Po nasvetu Horsta DJ6EV sem dodatno prvemu kristalu

dodal paralelno induktivnost 190nH in s tem popravil nesimetrijo filtra.

1.    Quarze und Quarzfilter von Horst DJ6EV Filter- Programm Dishal 2051. https://www.bartelsos.de/dk7jb.php/quarzfilter-horst.

2.    AADE Filter design: http://www.ke5fx.com/aadeflt.htm

Slika 7: Izračun parametrov filtra 

Opomba:  Vgradnja v postajo na lastno odgovornost. Priporočam le izkušenim z tehniškim znanjem. Za eventuelne napake ne odgovarjam. Za vse  ki nimajo tehniškega znanja in bi radi filter vgradili v postajo priporočam, da se obrnete na Jožeta S53PJ.

Yaesu FT 950 CW 1,4kHz roofing filter

After 2,7kHz roofing filter has been build in

 and succesfully tested in various contest,s  like WPX, Russian DX  Contest  and  CQWW160m  I have  decided to build narrower roofing filter which will be more suitable for CW.

                                        

I have chosen compromise between bandwith and filter 50 Ohm  impedance and therefore I have constructed 1,4 kHz wide roofing filter. BW -6dB  1497Hz  - 60dB  9284Hz. See pictures 2,3 and 4. The spectrum has been taken from   TP 1066   (see Service manual).  After the measurements I was suprised because measurments results are impresive on spacing 2 kHz. If I compare these results with Sherwood test,s  they are comparable with K3, TS 590SG  and   IC7610  Sherwood results. I allow  one or two  dB  tolerance in my measurements  because I am using ham equipment and no professional HP instruments as Sherwood did. A great help in construction this roofing filter has been  found in Horst Steder DJ6EV  article  » Monolitihic Crystal Filters » and his  » Crystal Ladder Filter Programm » Dishal« - See picture 1.  With  smaller changes this CW roofing filter can be used also in FT2K transceiver.

Measuring with :  1.st preamp OFF ; 500Hz Bandwith; Roofing 1,4KHz; AGC Off , Test band is 7MHz ;

MDS -127 dBm Noise floor

RMDR  (2kHz) 93 dB  (5kHz) 102dB

IMD3  (2kHz)  94dB    (5kHz)  95dB

Blocking  spacing 100 kHz : greater than 137 dB

 Lo noise spacing 10kHz : 139,9 dBc/Hz.

According to the experts’ opinion (e.g. Rob NC0B and Tom W8JI), the IMD DR3 of 85 dB is enough for CW. Thus my 2 kHz IMD DR3 94 dB results are excellent.

Picture 1:    Simulation CW filter with Dishal DJ6EV  programm

Picture 2 :  SSB and CW roofing filter connections

Picture 3 :  More than 60 dB filter ultimate attenuation

This  Filter Characteristic Diagram is comparable to the IC-7851 ---1.2kHz Optimum Roofing Filter.

Picture 4:    -6db  CW roofing filter bandwith

Picture 5: Measurments on 450kHz IF - TP 1054

I also  decided  to modify the AF passband. You can simply get rid of some hiss which sounds like a white noise  to roll off the highs with    820  pf  cap added parallel to capacitor C1571 . The receiver is now super quiet ( See picture 6 )

Picture 6 : AF modifications

The same Roofing  Filter can be  with minor changes used for up conversion receivers  with first  intermediate frequency (IF)  between 60 in 75 Mhz  like : 

        ICOM IC : 756, 765, 775, 7400, 7410, 7700,7850,7851

Kenwood  TS: 450, 850, 870, 950

                  Yaesu  FT :  450, 847, 897, 920, 1000D, 1000MP, 9000

Warning !!! Changing any hardware inside FT950 or FT2K will void your warranty. I am not responsible for any hardware failure. You made this mods on your own risk.! This modification requires a high level of soldering skill, possibly beyond that normally possessed by the average HAM. Professional assistance is advised if you are not confident that you have  this ability.