Message	Date	From	Subject
11718	2015-10-03 10:02:44	kg4rll	Switching Questions
General question about the best method to use for switching between the front end filters, crystal IF filters, BFO crystals etc..... What is the best method? Diodes? Relays? Transistors? Thanks, kg4rll
11719	2015-10-03 11:07:14	William Martin	Re: Switching Questions
kg4rll, I use 12 vdc enclosed dip relays. Simple cheap and reliable. Maybe not the best. I use them for switching oscillators and front end boards in my receiver project. I looked at using diodes and transistors for switching and it always seemed to increase the complexity of the overall project. I would be interested in what others have to say. With relays if you have a bad one you just pull it out of the dip socket and put a new one in. Bill N7EU   Sent from Bill's iPad 3  
11720	2015-10-03 12:51:31	kb1gmx	Re: Switching Questions
What is the best method? Diodes? Relays? Transistors? Yes. The all work and depending on layout and parts used likely about the same. You have to think about it and test to know. Its really about style, preferences, power consumption and my favorite what I have on hand. Allison
11721	2015-10-03 16:59:32	bob_ledoux	Re: Switching Questions
EMRFD page 6.62 states that measurements are required to maintain IMD performance when diode switches are used. PIN type diodes are recommended. Relays may be simpler. bob-N7SUR
11725	2015-10-03 20:15:03	kerrypwr	Re: Switching Questions
I've used the DIP reed relays to switch filters for a 5 MHz IF; they worked OK. For interest, I did some tests of insertion loss and isolation; Insertion loss; http://s15.postimg.org/v6rbnw75n/Reed_Relay_Insertion_Loss.jpg Isolation; http://s30.postimg.org/6cx1s1l0x/Reed_Relay_Isolation.jpg The DUT was a PRMA DPDT in a 14-pin (but with most pins omitted) DIL package. Kerry VK2TIL.
11730	2015-10-05 09:19:38	atlantaswl	Re: Switching Questions
Hi, I use 5V enclosed relays for bypass filter switching on the front end, and the same for switching in crystal filters. Seems to do a good job. Controlling multiple banks with the MAX4820 relay driver using SPI makes implementation pretty simple. 73, Fred KK4VEP
11731	2015-10-05 09:35:24	Dan Rae	Re: Switching Questions
Despite a number of replies in this thread advocating relays, I don't think anyone has yet pointed out the desirable use of "DC wetting" for low level signal circuits using relays which has been used in the telecoms field for many years. Look at the design of the front ends of pa3ake as well as the CDG2000 transceiver for examples. Also there is another possibility, that of using FET bus switches, see the BPF filters in the excellent Pic-A-Star design. Cheap and perform well. Dan - ac6ao
11732	2015-10-05 09:52:25	Dana Myers	Re: Switching Questions

11733	2015-10-05 11:25:05	Dana Myers	Re: Switching Questions

11734	2015-10-05 14:23:06	sohosources	Re: Switching Questions
Regarding dc whetting: When building switches for front-end filters, etc, the convenience of relays is high, while the extra parts counts for dc whetting seem to offset that convenience considerably. I was considering using DIP sockets (for the relays) in my designs (as another posted pointed out), which gives me the option of making an outboard "relay cleaner," which would pass the required dc current through the device while actuating it rapidly (10-50 Hz, depending on relay speed). The idea being to physically and electrically "clean" the internal contacts. My idea was to remove each relay once or twice a year to "thrash" them in the "relay rejuvinator," thereby eliminating any relay-based performance degradation. Any thoughts on whether this will work? :) Thanks, --Kirk, NT0Z My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon)
11741	2015-10-06 09:14:58	Mark Dunning	Re: Switching Questions
Kirt There were commercial relay contact cleaners on the market about 30 years ago that I know about, that passed a current of around 100mA through the relay's contacts while switching back and forth to clean them. They seemed to work okay as I recall. I think it would depend a lot on the contact surface materials. The relays I am talking about were high quality units with contact ratings of 5A. I think with small DIP style relays you probably run the risk of doing more damage, rather than good doing this. 73's Mark VK6WV

Message

Date

From

Subject

11718

2015-10-03 10:02:44

kg4rll

Switching Questions

General question about the best method to use for switching between the front end filters, crystal IF filters, BFO crystals etc.....

What is the best method? Diodes? Relays? Transistors?

Thanks,

kg4rll

11719

2015-10-03 11:07:14

William Martin

Re: Switching Questions

kg4rll,

I use 12 vdc enclosed dip relays. Simple cheap and reliable. Maybe not the best. I use them for switching oscillators and front end boards in my receiver project.

I looked at using diodes and transistors for switching and it always seemed to increase the complexity of the overall project.

I would be interested in what others have to say. With relays if you have a bad one you just pull it out of the dip socket and put a new one in.

Bill N7EU

  Sent from Bill's iPad 3  

11720

2015-10-03 12:51:31

kb1gmx

Re: Switching Questions

What is the best method? Diodes? Relays? Transistors?

Yes.

The all work and depending on layout and parts used likely about the same.

You have to think about it and test to know.

Its really about style, preferences, power consumption and my favorite

what I have on hand.

Allison

11721

2015-10-03 16:59:32

bob_ledoux

Re: Switching Questions

EMRFD page 6.62 states that measurements are required to maintain IMD performance when diode switches are used. PIN type diodes are recommended.

Relays may be simpler.

bob-N7SUR

11725

2015-10-03 20:15:03

kerrypwr

Re: Switching Questions

I've used the DIP reed relays to switch filters for a 5 MHz IF; they worked OK.

For interest, I did some tests of insertion loss and isolation;

Insertion loss;

http://s15.postimg.org/v6rbnw75n/Reed_Relay_Insertion_Loss.jpg

Isolation;

http://s30.postimg.org/6cx1s1l0x/Reed_Relay_Isolation.jpg

The DUT was a PRMA DPDT in a 14-pin (but with most pins omitted) DIL package.

Kerry VK2TIL.

11730

2015-10-05 09:19:38

atlantaswl

Re: Switching Questions

Hi,

I use 5V enclosed relays for bypass filter switching on the front end, and the same for switching in crystal filters. Seems to do a good job. Controlling multiple banks with the MAX4820 relay driver using SPI makes implementation pretty simple.

73,

Fred KK4VEP

11731

2015-10-05 09:35:24

Dan Rae

Re: Switching Questions

Despite a number of replies in this thread advocating relays, I don't
think anyone has yet pointed out the desirable use of "DC wetting" for
low level signal circuits using relays which has been used in the
telecoms field for many years. Look at the design of the front ends of
pa3ake as well as the CDG2000 transceiver for examples.

Also there is another possibility, that of using FET bus switches, see
the BPF filters in the excellent Pic-A-Star design. Cheap and perform well.

Dan - ac6ao

11732

2015-10-05 09:52:25

Dana Myers

Re: Switching Questions

11733

2015-10-05 11:25:05

Dana Myers

Re: Switching Questions

11734

2015-10-05 14:23:06

sohosources

Re: Switching Questions

Regarding dc whetting:

When building switches for front-end filters, etc, the convenience of relays is high, while the extra parts counts for dc whetting seem to offset that convenience considerably.

I was considering using DIP sockets (for the relays) in my designs (as another posted pointed out), which gives me the option of making an outboard "relay cleaner," which would pass the required dc current through the device while actuating it rapidly (10-50 Hz, depending on relay speed). The idea being to physically and electrically "clean" the internal contacts.

My idea was to remove each relay once or twice a year to "thrash" them in the "relay rejuvinator," thereby eliminating any relay-based performance degradation.

Any thoughts on whether this will work? :)

Thanks,

--Kirk, NT0Z

My book, "Stealth Amateur Radio," is now available from

www.stealthamateur.com and on the Amazon Kindle (soon)

11741

2015-10-06 09:14:58

Mark Dunning

Re: Switching Questions

Kirt

There were commercial relay contact cleaners on the market about 30
years ago that I know about, that passed a current of around 100mA
through the relay's contacts while switching back and forth to clean
them. They seemed to work okay as I recall.

I think it would depend a lot on the contact surface materials. The
relays I am talking about were high quality units with contact ratings
of 5A. I think with small DIP style relays you probably run the risk of
doing more damage, rather than good doing this.

73's Mark VK6WV