Keyboard Shortcuts
ctrl + shift + ? :
Show all keyboard shortcuts
ctrl + g :
Navigate to a group
ctrl + shift + f :
Find
ctrl + / :
Quick actions
esc to dismiss
Likes
- BITX20
- Messages
Search
|
Re: Components from Rapid Electronics
William Ford
开云体育Hans, I witheld my original cheque pending your
Email of today. I should like the full list as per your Email of 10.51 today and
will pay by Paypal as you suggest in uk pounds
Many thanks? jack ford G0tgp.
|
|
Re: linear coil
Hans Summers
Hi ashhar, sorry to bother you but, I was wanting to know if 3uH i calculated 3uH on each winding.Don't forget Mark, it's a bifilar transformer with two windings, not just a single winding with a centre tap. 73 Hans G0UPL |
|
Re: Fw: First QSO with the BITX20 Transceiver (fwd)
Hans Summers
The VFO and stabilizer are as large as the mainboard.Pete, what VFO stabilizer are you using? Is it Huff Puff? I love Huff Puff, and definitely intend to build a simple stabiliser for the BITX20 when I have the rest of it working. See my Huff Puff page for details: 73 Hans G0UPL |
|
Components from Rapid Electronics
Hans Summers
Finally here's a full list of what I can order for you from Rapid
Electronics . Prices are the Rapid prices, i.e. no profit for G0UPL :-( Postage is the price of a UK 1st class stamp for UK orders (?0.28). Other countries will be extra at cost. You must tell me your orders by this Wednesday at 13:00 UK time (12:00 GMT). I will order on Wednesday from Rapid, receive the components on Thursday, and send them out to you on Thursday. UK orders should receive them on Friday, ready for the weekend's homebrewing! Don't send any money yet, just tell me what you want and then wait until Wednesday when I have placed the order at Rapid: it might become slightly cheaper still if we go over other quantity pricing thresholds. You can pay me by any of the following methods: 1. Paypal (preferred) to my email address. Anyone can use a credit card to pay me this way, without needing to be a PayPal member, see . 2. UK cheque or postal order 3. Cash: British Pounds, or if you like approximate equivalent amounts in US Dollar or Euro. Not other currencies please, I am a homebrewer not a bank, I can't handle Mauritanian Ouguiya or Azerbaijanian Manat. If you are going to pay by 2 or 3 above, then I will send you my postal address via email. Rapid do not stock 2N2218 driver transistors, nor are they at Farnell . However I have managed to find a different source for supply of 2N2219A which is like the 2N2218 but has better gain specification. I'm sure it will be suitable. So here's the prices and description: feel free to take all items or only those you think you need. To keep it simple, transistors will be in a set of 25 BC547B, and diodes in a set of 15 1N4148. This leaves a couple of transistors and diodes left over for later modifications! If there's anything else you need particularly then let me know. Varying the quantity is fine too, e.g. take two IRF510's so you have a spare if you are worried about frying them, or if you want to play with push-pull for higher output power. Prices are in UK pounds inclusive of VAT (sales tax). ?3.58 Qty 10 of 10.000 MHz crystals, HC49 style ?0.59 Qty 25 of BC547B transistors ?0.70 2N2219A driver transistor ?1.53 IRF510 MOSFET ?0.19 Qty 15 of 1N4148 diodes ?0.07 36V Zener diode ?0.05 9.1V Zener diode ?0.05 5.6V Zener diode ?0.29 LM386N-1 Audio Amp IC (correct variety) ?1.88 Qty 5 of 2-22pF trimmer capacitor ?0.71 Miniature tuning capacitor* ?9.92 total, if you wanted everything and including ?0.28 UK postage. * NOTE: The tuning capacitor is one of the miniature kind as used in portable radios. Size is 20.2 x 20.2 x 10.8mm. Control shaft is 6.6mm diameter tapped with 2.6mm thread. Panel mounting is via twwo 2.6mm tapped screws next to the control shaft. Capacitance: AM section 3.0 - 141.6pF, Oscillator section 4.0 - 59.2pF. So in parallel you'd have 200pF which is less than Farhan's design for 350pF. It might therefore be necessary to alter the VFO coil to get the required tuning range. 73 Hans G0UPL |
|
Re: What are tap washers ?
ik1zyw
--- In BITX20@..., "Mark Jones" <Mark@H...> wrote:
Hi, just joined the group. Hope I will have some time to build this great RIG soon. Hmm, good question. An American asked me recently what a "jubileeclip" was - that was a struggle.water tap (faucet?) - like in the bathroom - so that when the water valve isUntil 10 minutes ago I never knew about "jubilee clips". Then I remembered our good friend Google has a good engine for searching images: Jubilee clip: Tap washer: Google images might help for other visual searches as well. Thanks for the explaination Mark, and sorry for the off-topic, Paolo |
|
Re: Low output
Ashhar Farhan
On Mon, 21 Jun 2004, david.g3ryp wrote:
I've taken the measurements you suggested and indeed it was the driver whose output was low - only about 1 volt peak. I was using BC549s throughout and although they tested ok when I changed them in the pre-driver and driver stages for 2n2369s the output from the driver went up to 4.5volts peak. Now where does this 6.3 volt resistor fit in? Am I looking at the wrong schematic? Perhaps in the driver emitters? I'll try changing the 10 ohms to 5.6 or thereabouts and see if the output goes up.The driver and prediver's emitter resistors are 6.2ohms (i used 5 ohms). due to the feedback design, individual transistor types are non-critical. the driver did require a heavier than BC147/2N3904 type of transistor. The plastic package prevents one from being able to gauge their heating by just touching them. until they are properly cooked. the 2N3866 will do fine. the latest 'build' of the circuit is on www.phonestack.com/farhan. - farhan Lastly thanks for putting a unit on the rf voltages. All too often schematics either don't contain rf voltages at all or they don't specify whether they're Peak to Peak or Peak or RMS - and there's quite a difference! |
|
Low output
david.g3ryp
开云体育Many thanks for the advice Farhan.
?
I've taken the measurements you suggested and
indeed it was the driver whose output was low - only about 1 volt peak. I was
using BC549s throughout and although they tested ok when I changed them in the
pre-driver and driver stages for 2n2369s the output from the driver went up to
4.5volts peak.
?
I've tried a variety of core types and none appears
to be critical. I'm using a t-50-6 in the IRF510 drain - 14 bifiliar turns to
get the 3uh you suggest. Know what you mean about winding these
things!
?
The output without the lpf in circuit is 6.25watts
but I need to adjust the bias for a standing current of rather more than 80ma to
achieve this - although it may be that the balanced mod is not that well
balanced (I haven't put in any caps yet).
I'll test this and let you know. Even without the
lpf the output is quite a pretty sine-wave.
?
Now where does this 6.3 volt resistor fit in? Am I
looking at the wrong schematic? Perhaps in the driver emitters? I'll try
changing the 10 ohms to 5.6 or thereabouts and see if the output goes
up.
?
Lastly thanks for putting a unit on the rf
voltages. All too often schematics either don't contain rf voltages at all or
they don't specify whether they're Peak to Peak or Peak or RMS - and there's
quite a difference!
?
I think I'll change the other 549s for 2n2369s if I
have enough just to see what happens.
?
Good luck to everyone.
?
David? |
|
Use 2N3866 instead of 2N2218
Ashhar Farhan
the 2N2218 is a fatter type of 2N2222. you can use the 2N3866 instead.
toggle quoted message
Show quoted text
they are expensive in india. but they might be easier to find elsewhere. - farhan On Mon, 21 Jun 2004, Hans Summers wrote:
Rapid do not stock 2N2218 driver transistors, nor are they at Farnell |
|
Re: Low Output (was Sunday)
ashhar_farhan
--- In BITX20@..., "david.g3ryp" <david.g3ryp@n...>
wrote: I wonder how much output everyone's getting from the IRF510?with the lpf in circuit. I've checked the lpf cut-off and I would expect some attenuation but not that much. I tried an irf530 which promptly overheated and destroyed itself as I increased the bias! hehe, david worry not. there are a couple of things that you ought to check. 1) cut the supply to the IRF510. then measure the RF output of the driver at 50 ohms resistors across the RIF510's gate. it should show 5 volts peak (that is 10 volts between the +ve and -ve swing). If you not are getting that much, then you have probably wired the output transformer incorrectly. they are probably in parallel to each other, or worse, the drain and the power supply are connected to the separate ends of the winding. check it carefully. 2) if you are not getting 5 volts at the 50 ohms resistor across the IRF510, then measure the output from the predriver. it should be a more than one volt peak (2 volts peak to peak on the 'scope). if either of these is a problem. check the following: a)that the collectors are showing somewhere north of 10 volts and the emitters are showing about 2 volts on both the driver and the predriver. b)if the DC voltages are alright, suspect that the AC connections are a problem. Most probably it is a mis-wired transformer. take them out of the circuit and check them carefully. i frequently make a mistake with shorting the opposite ends of the SAME wire and leaving the other wire in the pair isolated.d c) the 6.3 ohms, in my case is approximated by paralleling two 10 ohms. check that the 10 ohms IS 10 ohms and not 100 ohms. it is easy to confuse brown-black-brown with brown-black-black. above all, trace! measure the outputs at the RF fitler, pre-driver and the PA. tell us how much you get at each point. we will 'divide and conquer'. i dont know if i mentioned in the article that you should set the drain current to between 50 and 80mAs. I set it at 80mA, a bit on the higher side, but the linearity is better. - farhan |
|
Re: Substitutions or Sourcing components
Jon Harris
Thanks Hans, and many thanks for the offer of help, much
toggle quoted message
Show quoted text
appreciated! 73, Jon H. ----- Original Message -----
From: "Hans Summers" <Hans.Summers@...> To: <BITX20@...> Sent: Sunday, June 20, 2004 10:28 AM Subject: Re: [BITX20] Substitutions or Sourcing components Jon, I'll send you an email tomorrow with final details. 72/3 de Hans G0UPL -----Original Message----- From: Jon Harris <jon@...> To: BITX20@... <BITX20@...> Sent: Sat Jun 19 22:25:36 2004 Subject: Re: [BITX20] Substitutions or Sourcing components Sign me up too Hans, where do i send the cash! Cheers, Jon H. ----- Original Message ----- From: "Mark Jones" <Mark@...> To: <BITX20@...> Sent: Saturday, June 19, 2004 8:26 AM Subject: RE: [BITX20] Substitutions or Sourcing components Hi Hans Happy to go for a 6.21 order from you! Regards, Mark G0MGX -----Original Message----- From: Hans Summers [mailto:Hans.Summers@...] Sent: 18 June 2004 11:56 To: 'BITX20@...' Subject: RE: [BITX20] Substitutions or Sourcing components Keytronics has 10MHz xtals at ???1.00 each (ten required)I'm confused about the 2N3866 - what's it for? I see no mention on the circuit diagram; the nice thing is that a variety of transistors will do in this design. Rapid Electronics () sell 10MHz crystals at ???0.38 each (???0.45 incl sales tax). That drops to ???0.305 (???0.36 incl VAT) for QTY 25+. If enough people want them I'd be happy to order a batch and parcel them out. People who are interested in 10, let me know within the next few days and maybe we'll sort it out sometime next week. Assuming 25+, the price would be ???3.86 for 10 including a 1st class UK postage stamp (overseas postage stamp, extra). Ok look, I'm not going into the kit business but while we're at it, if you want them (also from Rapid): 25 BC547B's suitable for the rig: ???0.82 incl VAT 1 IRF510: ???1.53 incl VAT Presumably the total weight will be under 60g so these will all fit under the same single ???0.28 postage stamp. So, for a LIMITED TIME ONLY... Crystals, transistors and the MOSFET, ???6.21 incl UK postage (overseas is fine, we just add the extra postage). 72/3 Hans G0UPL Yahoo! Groups Sponsor ADVERTISEMENT < 001176/D=gr oups/S=1705063108:HM/EXP=1087642550/A=2128215/R=0/SIG=10se96mf6/* anion.yahoo.com> click here < D=groups/S= :HM/A=2128215/rand=403314333> _____ Yahoo! Groups Links * To visit your group on the web, go to: * To unsubscribe from this group, send an email to: BITX20-unsubscribe@... <mailto:BITX20-unsubscribe@...?subject=Unsubscribe> * Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <> . Yahoo! Groups Links Yahoo! Groups Sponsor ADVERTISEMENT ----------------------------------------------------------------- --------------- Yahoo! Groups Links a.. To visit your group on the web, go to: b.. To unsubscribe from this group, send an email to: BITX20-unsubscribe@... c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. |
|
Re: What are tap washers ?
Mark Jones
开云体育Hmm,
good question. An American asked me recently what a "jubilee clip" was - that
was a struggle.
?
A tap
washer is a thin shim of rubber/nylon/fibre that fits inside a water tap
(faucet?) - like in the bathroom - so that when the water valve is closed there
are no leaks.
?
Does
this help at all?
?
If
this doesn't help and you need some pictures of tap washers I can take some and
upload to the reflector?for you.
?
Maybe
we need a photo album called "what is a tap washer"
?
Mark. G0MGX
|
|
Re: We're off and running!
Hans Summers
Now the heat's really on at Hans Compoments Inc, then ;-)
toggle quoted message
Show quoted text
I used the tap washers for the inductors. Mine are a black rubbery type of material, I didn't find white nylon ones like Farhan's photos. It was fun to do things a bit "differently". I was not finding it so fun in the middle of 150 turns on the VFO coil but proud of the result when I'd finished. the GQRP club sell the FT37-43 toroidal cores which I used as per Farhan's recommendation in place of TV baluns. Club sales are for members only, ?0.75 per pack of 5 and they sell all the normal types too. There are calculators and toroid inductance charts all over the internet, a google search will find one immediately. I wonder if temperature stability will be better in the case of the tap washers than a ferrite core? 72/3 de Hans G0UPL -----Original Message-----
From: Mark <Mark@...> To: BITX20@... <BITX20@...> Sent: Sun Jun 20 13:19:36 2004 Subject: [BITX20] We're off and running! Hi All I've completed the VFO today, some pictures on the reflector. Just need to wait for Hans Components Inc before we go any further. VFO swinging from 4.25MHz to 4.4MHz - very adjustable with the trimmer. I used a fixed inductor of 22uH instead of the tap washer and 150 turns of 32swg - can't count that high. What are other people planning for inductor cores - is the general plan to proceed with tap washers or has anyone done the calcs for more conventional cores? Your comments welcome. Mark G0MGX Yahoo! Groups Links |
|
Sunday
david.g3ryp
开云体育I wonder how much output everyone's getting from
the IRF510?
?
I can get 2.5 watts rf maximum but this drops to
well under a watt with the lpf in circuit. I've checked the lpf cut-off and I
would expect some attenuation but not that much. I tried an irf530 which
promptly overheated and destroyed itself as I increased the bias!
?
I'm hopeless when it comes to getting rf out of
solid state stuff!
?
David |
|
Re: Fw: First QSO with the BITX20 Transceiver (fwd)
Ashhar Farhan
---------- Forwarded message ----------
Date: Sat, 19 Jun 2004 22:08:39 -0700 From: Pete Juliano <jessystems@...> To: Ashhar Farhan <farhan@...> Subject: Re: Fw: First QSO with the BITX20 Transceiver Hi Ashhar, For the crystal filter I am using 9.0 MHz computer crystals. I built a test oscillator and measured them with a frequency counter. Out of a group of 20, I found 4 that were within 50 hertz of each other. Those are the four in the radio. When I jumpered in a Commercial Filter to make a comparison, I didn't even have to touch up the carrier oscillator crystal so the HB filter has a very close center frequency to the commercial unit. The HB Filter does a nice job and is cheap --20 crystals cost me about $7 USD and within that remainder is another batch that could be used for a second filter. Attached are several photos of my version of the BITX20 including the Linear Amp, an overall view of the boards with digital display and a close up of the main circuit board. Hopefully next week I will have it all in a box. The VFO and stabilizer are as large as the mainboard. I used sockets for all of the semiconductors so I could do a little testing of various transistors and IC's The linear amp output filter has the following constants. 220PF, L1 which is 12 Turns of # 26SWG on an FT37-2 powdered iron core form (red core ~ 0.55 uhy). Then followed by a 220PF in parallel with a 330 PF (= 550 PF) followed by L2 same as L1 and then a 220 PF. The caps are ceramic on glass and rated at 100 volts. Really small caps. I used a 78L05 regulator and the bias adjust --I used what I had --a 25K ohm pot in parallel with a22K ohm resistor. Works fine. The linear amp board is 2inches X 2 inches (5CM X 5CM). You will note two relays --one at the linear amp just like the schematic --but I also had to resort to a relay at the main board as there was a RF feedback problem. The second relay solved that problem. The microphone is a low impedance --A D104 (lollipop) fitted with a Heil HC4 cartridge. I have a 25K ohm pot soldered right at mic connector and use that to set the mic gain. The last two evenings 20 meters has been hot and the RX is doing a FB job. Despite my initial comments about receiver sensitivity it is more than adequate. If I get a chance I may try my hand at an analog agc circuit. Again a very nice radio and despite its subtle simplicity --it packs a lot of peformance. I will keep you posted on my progress. 73's Pete W6JFR |
|
We're off and running!
Mark
Hi All
I've completed the VFO today, some pictures on the reflector. Just need to wait for Hans Components Inc before we go any further. VFO swinging from 4.25MHz to 4.4MHz - very adjustable with the trimmer. I used a fixed inductor of 22uH instead of the tap washer and 150 turns of 32swg - can't count that high. What are other people planning for inductor cores - is the general plan to proceed with tap washers or has anyone done the calcs for more conventional cores? Your comments welcome. Mark G0MGX |
|
Re: Substitutions or Sourcing components
Hans Summers
Jon, I'll send you an email tomorrow with final details. 72/3 de Hans G0UPL
toggle quoted message
Show quoted text
-----Original Message-----
From: Jon Harris <jon@...> To: BITX20@... <BITX20@...> Sent: Sat Jun 19 22:25:36 2004 Subject: Re: [BITX20] Substitutions or Sourcing components Sign me up too Hans, where do i send the cash! Cheers, Jon H. ----- Original Message ----- From: "Mark Jones" <Mark@...> To: <BITX20@...> Sent: Saturday, June 19, 2004 8:26 AM Subject: RE: [BITX20] Substitutions or Sourcing components Hi Hans Happy to go for a 6.21 order from you! Regards, Mark G0MGX -----Original Message----- From: Hans Summers [mailto:Hans.Summers@...] Sent: 18 June 2004 11:56 To: 'BITX20@...' Subject: RE: [BITX20] Substitutions or Sourcing components Keytronics has 10MHz xtals at ?1.00 each (ten required)I'm confused about the 2N3866 - what's it for? I see no mention on the circuit diagram; the nice thing is that a variety of transistors will do in this design. Rapid Electronics () sell 10MHz crystals at ?0.38 each (?0.45 incl sales tax). That drops to ?0.305 (?0.36 incl VAT) for QTY 25+. If enough people want them I'd be happy to order a batch and parcel them out. People who are interested in 10, let me know within the next few days and maybe we'll sort it out sometime next week. Assuming 25+, the price would be ?3.86 for 10 including a 1st class UK postage stamp (overseas postage stamp, extra). Ok look, I'm not going into the kit business but while we're at it, if you want them (also from Rapid): 25 BC547B's suitable for the rig: ?0.82 incl VAT 1 IRF510: ?1.53 incl VAT Presumably the total weight will be under 60g so these will all fit under the same single ?0.28 postage stamp. So, for a LIMITED TIME ONLY... Crystals, transistors and the MOSFET, ?6.21 incl UK postage (overseas is fine, we just add the extra postage). 72/3 Hans G0UPL Yahoo! Groups Sponsor ADVERTISEMENT < 001176/D=gr oups/S=1705063108:HM/EXP=1087642550/A=2128215/R=0/SIG=10se96mf6/* anion.yahoo.com> click here < D=groups/S= :HM/A=2128215/rand=403314333> _____ Yahoo! Groups Links * To visit your group on the web, go to: * To unsubscribe from this group, send an email to: BITX20-unsubscribe@... <mailto:BITX20-unsubscribe@...?subject=Unsubscribe> * Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <> . Yahoo! Groups Links |
|
Re: Substitutions or Sourcing components
Hans Summers
Please, do not send me any money yet! Now I have 6 orders, which takes us to
toggle quoted message
Show quoted text
the 100+ pricing for the BC547B so everything will become slightly cheaper. Thanks for your emails, I will reply individually as soon as I get the chance, which probably won't be until Monday. It's nice to see so many people joining this group and planning to build this neat design. I'm happy to extend my offer of bulk purchase components from Rapid Electronics to optionally include for those who want them, some of the other parts which you might not find so easily in your junk boxes. I'm thinking of the 9V1 and 36V zener diodes, 7805 voltage regulator, 10x 1N4148 diodes, trimmer capacitors, and possibly something to substitute the 2N2218 driver transistor. All small components which won't much increase the weight, and will still mean I can use small envelopes and not worry about special packaging etc. I'll work out prices on Monday at my office, which is where my Rapid Electronics catalogue resides ;-) In his prior version Farhan was using two BC547 parallelled, and only replaced them with a single heatsinked 2N2218 when the '547's were fried during a long PSK31 QSO. Can Farhan or anybody else suggest alternatives since I don't think Rapid sell the 2N2218? Now a word about the crystals. Farhan recommends buying 10 and choosing the closest 4 for the filter. I did so and chose the next closest one for the BFO though this wouldn't really be critical. Measurement could be via a frequency counter or zero beating on another receiver with digital readout and coverage of 10MHz. I have a homebrewed counter in my HF receiver, you can read about it on my webpage. But if you don't have either of those items I can imagine a rather simple and cheap frequency counter circuit having only 3 common 74HC-series IC's and a handful of LED's for binary readout of frequency, providing more than sufficient resolution for the task. Failing all of that I'd seriously suggest getting just 5 crystals and trying them anyway. When I measured my 10 they were quite close and I think reasonable results would be obtainable without the precise matching if suitable equipment isn't available. I'm interested in other people's opinion on this. If I can manage to find my notes on Monday I'll post my ten measurements, and you'll see what I mean. Any more orders, let me know via email. But remember, no money yet until I make final calculations. 72/3 Hans G0UPL -----Original Message-----
From: Jon Harris <jon@...> To: BITX20@... <BITX20@...> Sent: Sat Jun 19 22:25:36 2004 Subject: Re: [BITX20] Substitutions or Sourcing components Sign me up too Hans, where do i send the cash! Cheers, Jon H. ----- Original Message ----- From: "Mark Jones" <Mark@...> To: <BITX20@...> Sent: Saturday, June 19, 2004 8:26 AM Subject: RE: [BITX20] Substitutions or Sourcing components Hi Hans Happy to go for a 6.21 order from you! Regards, Mark G0MGX -----Original Message----- From: Hans Summers [mailto:Hans.Summers@...] Sent: 18 June 2004 11:56 To: 'BITX20@...' Subject: RE: [BITX20] Substitutions or Sourcing components Keytronics has 10MHz xtals at ?1.00 each (ten required)I'm confused about the 2N3866 - what's it for? I see no mention on the circuit diagram; the nice thing is that a variety of transistors will do in this design. Rapid Electronics () sell 10MHz crystals at ?0.38 each (?0.45 incl sales tax). That drops to ?0.305 (?0.36 incl VAT) for QTY 25+. If enough people want them I'd be happy to order a batch and parcel them out. People who are interested in 10, let me know within the next few days and maybe we'll sort it out sometime next week. Assuming 25+, the price would be ?3.86 for 10 including a 1st class UK postage stamp (overseas postage stamp, extra). Ok look, I'm not going into the kit business but while we're at it, if you want them (also from Rapid): 25 BC547B's suitable for the rig: ?0.82 incl VAT 1 IRF510: ?1.53 incl VAT Presumably the total weight will be under 60g so these will all fit under the same single ?0.28 postage stamp. So, for a LIMITED TIME ONLY... Crystals, transistors and the MOSFET, ?6.21 incl UK postage (overseas is fine, we just add the extra postage). 72/3 Hans G0UPL Yahoo! Groups Sponsor ADVERTISEMENT < 001176/D=gr oups/S=1705063108:HM/EXP=1087642550/A=2128215/R=0/SIG=10se96mf6/* anion.yahoo.com> click here < D=groups/S= :HM/A=2128215/rand=403314333> _____ Yahoo! Groups Links * To visit your group on the web, go to: * To unsubscribe from this group, send an email to: BITX20-unsubscribe@... <mailto:BITX20-unsubscribe@...?subject=Unsubscribe> * Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <> . Yahoo! Groups Links |
to navigate to use esc to dismiss